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  • 101. Karlsson, M
    et al.
    Brandberg, J
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Loyd, Dan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Computer simulation for improved assessment of mitral regurgitation.1997Ingår i: COMPUTERS IN CARDIOLOGY 1997, VOL 24, 1997, Vol. 24, s. 169-170Konferensbidrag (Refereegranskat)
    Abstract [en]

    Since valvular regurgitation is one of the most common malfunctions of the heart the quantification of valvular regurgitation by means of non-invasive methods is desired. However existing methods for quantitative assessment is far from perfect. The aim of this paper is to study the proximal velocity field for non-stationary flow and non-planar geometries by computer simulation, which were performed using the FIDAP package to numerically solve the governing equations. A plexiglass in-vitro model similar to the computer model was used for comparison and the same results were obtained. We have found that it is possible to refine the PISA method and standardize flow calculations. Further improvements will hopefully create a tool for the echocardiographer that will facilitate evaluation and clinical applicability of the PISA approach.

  • 102.
    Karlsson, M G Daniel
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Hübbert, Laila
    Östergötlands Läns Landsting, Hjärtcentrum.
    Lönn, Urban
    Östergötlands Läns Landsting, Hjärtcentrum.
    Janerot-Sjöberg, Birgitta
    Östergötlands Läns Landsting, Hjärtcentrum.
    Ahn, Henrik Casimir
    Östergötlands Läns Landsting, Hjärtcentrum.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Myocardial tissue motion influence on laser Doppler perfusion monitoring using tissue Doppler imaging2004Ingår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 42, nr 6, s. 770-776Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tissue motion of the beating heart generates large movement artifacts in the laser Doppler perfusion monitoring (LDPM) signal. The aim of the study was to use tissue Doppler imaging (TDI) to localise intervals during the cardiac cycle where the influence of movement artifacts on the LDPM signal is minimum. TDI velocities and LDPM signals were investigated on three calves, for normal heartbeat and during occlusion of the left anterior descending coronary artery. Intervals of low tissue velocity (TDIint<1 cm s−1) during the cardiac cycle were identified. During occlusion, these intervals were compared with low LDPM signal intervals (LDPMint<50% compared with baseline). Low-velocity intervals were found in late systole (normal and occlusion) and late diastole (normal). Systolic intervals were longer and less sensitive to heart rate variation compared with diastolic ones. The overlap between LDPMint and TDIint in relation to TDIint length was 84±27% (n=14). The LDPM signal was significantly (p<0.001, n=14) lower during occlusion if calculated during minimum tissue motion inside TDIint), compared with averaging over the entire cardiac cycle without taking tissue motion into consideration. In conclusion, movement artifacts are reduced if the LDPM signal is correlated to the ECG and investigated during minimum wall motion. The optimum interval depends on the application; late systole and late diastole can be used.

  • 103.
    Karlsson, Markus
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Forsgren, Mikael
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Medicinska fakulteten. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Region Östergötland, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Dahlström, Nils
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Leinhard Dahlqvist, Olof
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Medicinska fakulteten.
    Norén, Bengt
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Ekstedt, Mattias
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Hjärt- och Medicincentrum, Magtarmmedicinska kliniken.
    Kechagias, Stergios
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Hjärt- och Medicincentrum, Magtarmmedicinska kliniken.
    Lundberg, Peter
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Diffuse Liver Disease: Measurements of Liver Trace Metal Concentrations and R2* Relaxation Rates2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Introduction

    Over the past decade, several methods for measuring of liver iron content (LIC) non-invasively with MRI have been developed and verified. The most promising methods uses relaxometry, measuring either R2- or R2* relaxation rate in the liver1,2. For instance, several studies have shown that there seems to be a linear relationship between R2* and LIC1. However, few of these studies have measured the liver content of other metals, which could also affect the relaxation rates. The goal of this study was to investigate if any trace metals, other than iron could affect the R2* relaxation rate in liver tissue in a patients with diffuse liver disease.

    Subjects and methods

    75 patients with suspected diffuse liver disease underwent an MRI examination followed by a liver biopsy the same day. The R2* relaxation rate of the water protons in the liver was measured using an axial 3D multi-slice fat-saturated multi-echo turbo field echo sequence (TE=4.60/9.20/13.80/18.40/23.00ms). Regions of interest (ROI) were drawn and R2* was estimated by fitting the mean signal intensity from the ROIs to a mono-exponential decay model. The biopsies were freeze dried and the concentrations of iron, manganese, copper, cobalt and gadolinium were measured using Inductively Coupled Plasma Sector Field Mass Spectrometry (ICP-SFMS). A multiple linear regression analysis was applied to determine which of the measured metals significantly affected the relaxation rate.

    Results

    A linear regression with the LIC and R2* showed a reasonable fit (Figure 1). The multiple linear regression analysis (Table 1) showed that iron as well as manganese had a significant affect on R2*. Unlike iron however, the regression coefficient of manganese was negative, meaning that an increasing manganese concentration gave a shorter R2* relaxation rate. The same trend can be seen when plotting the manganese concentration against R2* (Figure 2).

  • 104. Beställ onlineKöp publikationen >>
    Kok, Manon
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Probabilistic modeling for sensor fusion with inertial measurements2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In recent years, inertial sensors have undergone major developments. The quality of their measurements has improved while their cost has decreased, leading to an increase in availability. They can be found in stand-alone sensor units, so-called inertial measurement units, but are nowadays also present in for instance any modern smartphone, in Wii controllers and in virtual reality headsets.

    The term inertial sensor refers to the combination of accelerometers and gyroscopes. These measure the external specific force and the angular velocity, respectively. Integration of their measurements provides information about the sensor's position and orientation. However, the position and orientation estimates obtained by simple integration suffer from drift and are therefore only accurate on a short time scale. In order to improve these estimates, we combine the inertial sensors with additional sensors and models. To combine these different sources of information, also called sensor fusion, we make use of probabilistic models to take the uncertainty of the different sources of information into account. The first contribution of this thesis is a tutorial paper that describes the signal processing foundations underlying position and orientation estimation using inertial sensors.

    In a second contribution, we use data from multiple inertial sensors placed on the human body to estimate the body's pose. A biomechanical model encodes the knowledge about how the different body segments are connected to each other. We also show how the structure inherent to this problem can be exploited. This opens up for processing long data sets and for solving the problem in a distributed manner.

    Inertial sensors can also be combined with time of arrival measurements from an ultrawideband (UWB) system. We focus both on calibration of the UWB setup and on sensor fusion of the inertial and UWB measurements. The UWB measurements are modeled by a tailored heavy-tailed asymmetric distribution. This distribution naturally handles the possibility of measurement delays due to multipath and non-line-of-sight conditions while not allowing for the possibility of measurements arriving early, i.e. traveling faster than the speed of light.

    Finally, inertial sensors can be combined with magnetometers. We derive an algorithm that can calibrate a magnetometer for the presence of metallic objects attached to the sensor. Furthermore, the presence of metallic objects in the environment can be exploited by using them as a source of position information. We present a method to build maps of the indoor magnetic field and experimentally show that if a map of the magnetic field is available, accurate position estimates can be obtained by combining inertial and magnetometer measurements.

    Delarbeten
    1. Using Inertial Sensors for Position and Orientation Estimation
    Öppna denna publikation i ny flik eller fönster >>Using Inertial Sensors for Position and Orientation Estimation
    2017 (Engelska)Ingår i: Foundations and Trends® in Signal Processing, ISSN 1932-8346, nr 1-2, s. 166s. 1-153Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Microelectromechanical system (MEMS) inertial sensors have become ubiquitous in modern society. Built into mobile telephones, gaming consoles, virtual reality headsets, we use such sensors on a daily basis. They also have applications in medical therapy devices, motion-capture filming, traffic monitoring systems, and drones. While providing accurate measurements over short time scales, this diminishes over longer periods. To date, this problem has been resolved by combining them with additional sensors and models. This adds both expense and size to the devices. This tutorial focuses on the signal processing aspects of position and orientation estimation using inertial sensors. It discusses different modelling choices and a selected number of important algorithms that engineers can use to select the best options for their designs. The algorithms include optimization-based smoothing and filtering as well as computationally cheaper extended Kalman filter and complementary filter implementations. Engineers, researchers, and students deploying MEMS inertial sensors will find that this tutorial is an essential monograph on how to optimize their designs.

    Ort, förlag, år, upplaga, sidor
    Boston, Delft: Now Publishers Inc., 2017. s. 166
    Nyckelord
    Sensor and multiple source signal processing, Filtering, Estimation, Identification, Sensors and Estimation
    Nationell ämneskategori
    Reglerteknik
    Identifikatorer
    urn:nbn:se:liu:diva-150519 (URN)10.1561/2000000094 (DOI)9781680833560 (ISBN)9781680833577 (ISBN)
    Tillgänglig från: 2018-08-24 Skapad: 2018-08-24 Senast uppdaterad: 2018-08-24Bibliografiskt granskad
    2. An optimization-based approach to human body motion capture using inertial sensors
    Öppna denna publikation i ny flik eller fönster >>An optimization-based approach to human body motion capture using inertial sensors
    2014 (Engelska)Ingår i: Proceedings of the 19th IFAC World Congress, 2014 / [ed] Boje, Edward; Xia, Xiaohua, International Federation of Automatic Control , 2014, s. 79-85Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    In inertial human motion capture, a multitude of body segments are equipped with inertial measurement units, consisting of 3D accelerometers, 3D gyroscopes and 3D magnetometers. Relative position and orientation estimates can be obtained using the inertial data together with a biomechanical model. In this work we present an optimization-based solution to magnetometer-free inertial motion capture. It allows for natural inclusion of biomechanical constraints, for handling of nonlinearities and for using all data in obtaining an estimate. As a proof-of-concept we apply our algorithm to a lower body configuration, illustrating that the estimates are drift-free and match the joint angles from an optical reference system.

    Ort, förlag, år, upplaga, sidor
    International Federation of Automatic Control, 2014
    Serie
    World Congress, ISSN 1474-6670 ; World Congress, Volume# 19 | Part# 1
    Nyckelord
    Human body motion capture, optimization, maximum a posteriori estimation, inertial sensors, 6D pose estimation.
    Nationell ämneskategori
    Reglerteknik
    Identifikatorer
    urn:nbn:se:liu:diva-111543 (URN)10.3182/20140824-6-ZA-1003.02252 (DOI)978-3-902823-62-5 (ISBN)
    Konferens
    19th World Congress of the International Federation of Automatic Control (IFAC), Cape Town, South Africa, August 24-29, 2014
    Projekt
    MC ImpulseCADICSBALANCE
    Forskningsfinansiär
    EU, FP7, Sjunde ramprogrammet, 1933031801Vetenskapsrådet, 1933011102
    Tillgänglig från: 2014-10-22 Skapad: 2014-10-22 Senast uppdaterad: 2016-12-15Bibliografiskt granskad
    3. A Scalable and Distributed Solution to the Inertial Motion Capture Problem
    Öppna denna publikation i ny flik eller fönster >>A Scalable and Distributed Solution to the Inertial Motion Capture Problem
    Visa övriga...
    2016 (Engelska)Ingår i: Proceedings of the 19th International Conference on Information Fusion, Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 1348-1355Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    In inertial motion capture, a multitude of body segments are equipped with inertial sensors, consisting of 3D accelerometers and 3D gyroscopes. Using an optimization-based approach to solve the motion capture problem allows for natural inclusion of biomechanical constraints and for modeling the connection of the body segments at the joint locations. The computational complexity of solving this problem grows both with the length of the data set and with the number of sensors and body segments considered. In this work, we present a scalable and distributed solution to this problem using tailored message passing, capable of exploiting the structure that is inherent in the problem. As a proof-of-concept we apply our algorithm to data from a lower body configuration. 

    Ort, förlag, år, upplaga, sidor
    Institute of Electrical and Electronics Engineers (IEEE), 2016
    Nationell ämneskategori
    Reglerteknik
    Identifikatorer
    urn:nbn:se:liu:diva-130555 (URN)000391273400178 ()978-0-9964-5274-8 (ISBN)
    Konferens
    19th International Conference on Information Fusion, Heidelberg, Germany, July 5-8, 2016
    Projekt
    CADICSELLIITThe project Probabilistic modeling of dynamical systems (Contract number: 621- 2013-5524)
    Forskningsfinansiär
    VetenskapsrådetELLIIT - The Linköping‐Lund Initiative on IT and Mobile Communications
    Tillgänglig från: 2016-08-16 Skapad: 2016-08-16 Senast uppdaterad: 2017-02-03
    4. Indoor Positioning Using Ultrawideband and Inertial Measurements
    Öppna denna publikation i ny flik eller fönster >>Indoor Positioning Using Ultrawideband and Inertial Measurements
    2015 (Engelska)Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 64, nr 4, s. 1293-1303Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    In this paper, we present an approach to combine measurements from inertial sensors (accelerometers and gyroscopes) with time-of-arrival measurements from an ultrawideband (UWB) system for indoor positioning. Our algorithm uses a tightly coupled sensor fusion approach, where we formulate the problem as a maximum a posteriori (MAP) problem that is solved using an optimization approach. It is shown to lead to accurate 6-D position and orientation estimates when compared to reference data from an independent optical tracking system. To be able to obtain position information from the UWB measurements, it is imperative that accurate estimates of the UWB receivers positions and their clock offsets are available. Hence, we also present an easy-to-use algorithm to calibrate the UWB system using a maximum-likelihood (ML) formulation. Throughout this work, the UWB measurements are modeled by a tailored heavy-tailed asymmetric distribution to account for measurement outliers. The heavy-tailed asymmetric distribution works well on experimental data, as shown by analyzing the position estimates obtained using the UWB measurements via a novel multilateration approach.

    Ort, förlag, år, upplaga, sidor
    Institute of Electrical and Electronics Engineers (IEEE), 2015
    Nyckelord
    Calibration; heavy-tailed noise distribution; inertial sensors; sensor fusion; ultrawideband (UWB)
    Nationell ämneskategori
    Elektroteknik och elektronik
    Identifikatorer
    urn:nbn:se:liu:diva-118060 (URN)10.1109/TVT.2015.2396640 (DOI)000353111900004 ()
    Anmärkning

    Funding Agencies|Control, Autonomy, and Decision-making In Complex Systems (CADICS): a Linnaeus Center - Swedish Research Council (VR); BALANCE: a European Commission FP7 Research Project; Swedish Research Council (VR) [621-2013-5524]

    Tillgänglig från: 2015-05-20 Skapad: 2015-05-20 Senast uppdaterad: 2017-12-04
    5. Magnetometer calibration using inertial sensors
    Öppna denna publikation i ny flik eller fönster >>Magnetometer calibration using inertial sensors
    2016 (Engelska)Ingår i: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 16, nr 14, s. 5679-5689Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    In this work we present a practical calibration algorithm that calibrates a magnetometer using inertial sensors. The calibration corrects for magnetometer sensor errors, for the presence of magnetic disturbances and for misalignment between the magnetometer and the inertial sensor axes. It is based on a maximum likelihood formulation and is formulated as an offline method. It is shown to give good results using data from two different commercially available sensor units. Using the calibrated magnetometer measurements in combination with the inertial sensors to determine orientation, is shown to lead to significantly improved heading estimates.

    Ort, förlag, år, upplaga, sidor
    Institute of Electrical and Electronics Engineers (IEEE), 2016
    Nationell ämneskategori
    Reglerteknik
    Identifikatorer
    urn:nbn:se:liu:diva-106879 (URN)10.1109/JSEN.2016.2569160 (DOI)000379601600024 ()
    Anmärkning

    Funding agencies: Funding Agencies|CADICS; Project Probabilistic Modeling of Dynamical Systems through the Swedish Research Council (Vetenskapsradet) [621-2013-5524]; MC Impulse through the European Commission Seventh Framework Programme Research Project; Linnaeus Center through the Swedish Research Council (Vetenskapsradet)

    Vid tiden för disputation förelåg publikationen som manuskript

    Tillgänglig från: 2014-05-23 Skapad: 2014-05-23 Senast uppdaterad: 2017-12-05
    6. Modeling and Interpolation of the Ambient Magnetic Field by Gaussian Processes
    Öppna denna publikation i ny flik eller fönster >>Modeling and Interpolation of the Ambient Magnetic Field by Gaussian Processes
    Visa övriga...
    2018 (Engelska)Ingår i: IEEE Transactions on robotics, ISSN 1552-3098, E-ISSN 1941-0468, Vol. 34, nr 4, s. 1112-1127Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Anomalies in the ambient magnetic field can be used as features in indoor positioning and navigation. By using Maxwell’s equations, we derive and present a Bayesian nonparametric probabilistic modeling approach for interpolation and extrapolation of the magnetic field. We model the magnetic field components jointly by imposing a Gaussian process (GP) prior to the latent scalar potential of the magnetic field. By rewriting the GP model in terms of a Hilbert space representation, we circumvent the computational pitfalls associated with GP modeling and provide a computationally efficient and physically justified modeling tool for the ambient magnetic field. The model allows for sequential updating of the estimate and time-dependent changes in the magnetic field. The model is shown to work well in practice in different applications. We demonstrate mapping of the magnetic field both with an inexpensive Raspberry Pi powered robot and on foot using a standard smartphone.

    Ort, förlag, år, upplaga, sidor
    Institute of Electrical and Electronics Engineers (IEEE), 2018
    Nyckelord
    Magnetometers;Magnetic domains;Magnetosphere;Computational modeling;Interpolation;Mathematical model;Simultaneous localization and mapping;Gaussian process (GP);magnetic field;mapping;Maxwell’s equations;online representation
    Nationell ämneskategori
    Reglerteknik
    Identifikatorer
    urn:nbn:se:liu:diva-150520 (URN)10.1109/TRO.2018.2830326 (DOI)
    Tillgänglig från: 2018-08-24 Skapad: 2018-08-24 Senast uppdaterad: 2018-08-24Bibliografiskt granskad
    7. MEMS-based inertial navigation based on a magnetic field map
    Öppna denna publikation i ny flik eller fönster >>MEMS-based inertial navigation based on a magnetic field map
    2013 (Engelska)Ingår i: Proceedings of the 38th International Conference on Acoustics, Speech, and Signal Processing (ICASSP), 2013, s. 6466-6470Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    This paper presents an approach for 6D pose estimation where MEMS inertial measurements are complemented with magnetometer measurements assuming that a model (map) of the magnetic field is known. The resulting estimation problem is solved using a Rao-Blackwellized particle filter. In our experimental study the magnetic field is generated by a magnetic coil giving rise to a magnetic field that we can model using analytical expressions. The experimental results show that accurate position estimates can be obtained in the vicinity of the coil, where the magnetic field is strong.

    Nyckelord
    Magnetic field, inertial navigation, state estimation, Rao-Blackwellized particle filter, magnetometer
    Nationell ämneskategori
    Reglerteknik Signalbehandling
    Identifikatorer
    urn:nbn:se:liu:diva-102632 (URN)10.1109/ICASSP.2013.6638911 (DOI)000329611506126 ()
    Konferens
    The 38th International Conference on Acoustics, Speech, and Signal Processing (ICASSP), Vancouver, Canada, May 26-31, 2013
    Forskningsfinansiär
    EU, FP7, Sjunde ramprogrammet, 1933031801Vetenskapsrådet, 1933011102
    Tillgänglig från: 2013-12-17 Skapad: 2013-12-17 Senast uppdaterad: 2016-12-15
    Ladda ner fulltext (pdf)
    Probabilistic modeling for sensor fusion with inertial measurements
    Ladda ner (pdf)
    omslag
    Ladda ner (jpg)
    presentationsbild
  • 105.
    Kågedal, Bertil
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Klinisk kemi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Laboratoriemedicinskt centrum, Klinisk kemi.
    Detecting Minimal Residual Disease in Neuroblastoma: Still a Ways to Go2009Ingår i: Clinical Chemistry, ISSN 0009-9147, E-ISSN 1530-8561, Vol. 55, nr 7, s. 1268-1270Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    n/a

  • 106.
    Larsson, Jonatan
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik.
    Implementation and evaluation of motion correction for quantitative MRI2010Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Image registration is the process of aligning two images such that their mutual features overlap. This is of great importance in several medical applications. In 2008 a novel method for simultaneous T1, T2 and proton density quantification was suggested. The method is in the field of quantitative Magnetic Resonance Imaging or qMRI. In qMRI parameters are quantified by a pixel-to-pixel fit of the image intensity as a function of different MR scanner settings. The quantification depends on several volumes of different intensities to be aligned. If a patient moves during the data aquisition the datasets will not be aligned and the results are degraded due to this. Since the quantification takes several minutes there is a considerable risk of patient movements. In this master thesis three image registration methods are presented and a comparison in robustness and speed was made. The phase based algorithm was suited for this problem and limited to finding rigid motion. The other two registration algorithms, originating from the Statistical Parametrical Mapping, SPM, package, were used as references. The result shows that the pixel-to-pixel fit is greatly improved in the datasets with found motion. In the comparison between the different methods the phase based algorithm turned out to be both the fastest and the most robust method.

    Ladda ner fulltext (pdf)
    master_thesis_jonatan_larsson
  • 107. Beställ onlineKöp publikationen >>
    Latorre, Malcolm
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    The Physical Axon: Modeling, Simulation and Electrode Evaluation2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Elektroder används inom sjukvården, både för att mäta biologiska signaler, t.ex. hjärtats aktivitet med EKG, eller för att stimulera vävnad, t.ex. vid djup hjärnstimulering (DBS). För båda användningsområdena är det viktigt med en grundläggande förståelse av elektrodens interaktion med vävnaden. Det finns ingen standardiserad metod för att utvärdera medicinsk elektroders dataöverföringsfunktion. I den här avhandlingen presenteras en metod för att underlätta elektrodtestning. En hårdvarumodell av ett axon (Paxon) har utvecklats. Paxon kan programmeras för att efterlikna repeterbara aktionspotentialer från en perifer nerv. Längs axonet finns 40 noder, vilka var och en består av en tunn (20 μm) guldtråd inbäddad i harts och därefter kopplad till elektronik. Denna testbädd har använts för att undersöka EKG elektroders egenskaper. EKG elektroderna visade på variationer i orientering och position i relation till Paxon. Detta har en direkt inverkan på den registrerade signalen. Även andra elektrotyper kan testas i Paxon, t.ex. DBS elektroder.

    En teoretisk jämförelse mellan två neuronmodeller med olika komplexitet, anpassade för användning vid DBS studier, har utförts. Modellerna konfigurerades för att studera inverkan på aktiveringsavstånd från olika axondiametrar, stimulationspuls och stimulationsstyrka. Då båda modellerna visade likvärdiga aktiveringsavstånd och beräkningstid så förordas den enklare neuronmodellen för DBS simuleringar. En enklare modell kan lättare introduceras i klinisk verksamhet. Simuleringarna stöder tidigare resultat som visat att det elektriska fältet är en bra parameter för presentation av resultat vid simulering av DBS. Metoden exemplifieras vid simulering av aktiveringsavstånd och elektriska fältets utbredning för olika typer av DBS elektroder i en patient-specifik studie.

    Delarbeten
    1. A Physical Action Potential Generator: Design, Implementation and Evaluation
    Öppna denna publikation i ny flik eller fönster >>A Physical Action Potential Generator: Design, Implementation and Evaluation
    2015 (Engelska)Ingår i: Frontiers in Neuroscience, ISSN 1662-4548, E-ISSN 1662-453X, Vol. 9, s. 1-11, artikel-id 371Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The objective was to develop a physical action potential generator (Paxon) with the ability to generate a stable, repeatable, programmable, and physiological-like action potential. The Paxon has an equivalent of 40 nodes of Ranvier that were mimicked using resin embedded gold wires (Ø = 20 μm). These nodes were software controlled and the action potentials were initiated by a start trigger. Clinically used Ag-AgCl electrodes were coupled to the Paxon for functional testing. The Paxon’s action potential parameters were tunable using a second order mathematical equation to generate physiologically relevant output, which was accomplished by varying the number of nodes involved (1 to 40 in incremental steps of 1) and the node drive potential (0 to 2.8V in 0.7 mV steps), while keeping a fixed inter-nodal timing and test electrode configuration. A system noise floor of 0.07 ± 0.01 μV was calculated over 50 runs. A differential test electrode recorded a peak positive amplitude of 1.5 ± 0.05 mV (gain of 40x) at time 196.4 ± 0.06 ms, including a post trigger delay. The Paxon’s programmable action potential like signal has the possibility to be used as a validation test platform for medical surface electrodes and their attached systems.

    Ort, förlag, år, upplaga, sidor
    Frontiers Research Foundation, 2015
    Nyckelord
    Action potential, biomedical electrode, electronic nerve model, nodes of Ranvier, ulnar nerve
    Nationell ämneskategori
    Medicinteknik
    Identifikatorer
    urn:nbn:se:liu:diva-121086 (URN)10.3389/fnins.2015.00371 (DOI)
    Anmärkning

    Funding agencies| Linköping University; the Swedish Research Council (Grant No. 621-2013-6078)

    At the time for thesis presentation publication was in status: Manuscript

    Tillgänglig från: 2015-09-07 Skapad: 2015-09-07 Senast uppdaterad: 2017-12-04Bibliografiskt granskad
    2. Describing Measurement Behaviour of a Surface Ag-AgCl Electrode Using the Paxon Test Platform
    Öppna denna publikation i ny flik eller fönster >>Describing Measurement Behaviour of a Surface Ag-AgCl Electrode Using the Paxon Test Platform
    2016 (Engelska)Ingår i: XIV MEDITERRANEAN CONFERENCE ON MEDICAL AND BIOLOGICAL ENGINEERING AND COMPUTING 2016, SPRINGER , 2016, Vol. 57, s. 442-445Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    A better understanding of bioelectrodes can be acquired with extended testing, which will lead to better methodology and data quality. Today electrodes are evaluated for intraelectrode differences and performance with a traditional gain-phase method, while using the physical axon action potential generator (Paxon) test platform offers extended test possibilities. The direct gain-phase measurements are useful to extract the transfer function of the electrode, as well as some other base parameters. The Paxon test platform is a complementary method that tests electrodes under conditions that are more realistic, mimicking real measurement situations in comparison to the gain-phase method. The Paxon also allows tests to be performed beyond what the gain-phase methods can measure, for example electrode rotation, which would uncover variations in the symmetry of the electrode. When tested, the symmetry properties of the electrode, where the electrodes are rotated in steps of 90 degrees, resulted in a peak to peak variation in detected amplitude of 5.3 +/- 8.9 mV. Therefore, the Paxon appears to be a feasible test platform for characterizing electrodes beyond the gain-phase tests in a semiautomatic manner.

    Ort, förlag, år, upplaga, sidor
    SPRINGER, 2016
    Serie
    IFMBE Proceedings, ISSN 1680-0737
    Nyckelord
    Electrode testing; Characterization; Coupling Parameters; Stability test; Axon potential
    Nationell ämneskategori
    Medicinsk apparatteknik
    Identifikatorer
    urn:nbn:se:liu:diva-129510 (URN)10.1007/978-3-319-32703-7_86 (DOI)000376283000086 ()978-3-319-32703-7 (ISBN)978-3-319-32701-3 (ISBN)
    Konferens
    14th Mediterranean Conference on Medical and Biological Engineering and Computing (MEDICON)
    Tillgänglig från: 2016-06-20 Skapad: 2016-06-20 Senast uppdaterad: 2017-06-19Bibliografiskt granskad
    3. Investigation into Deep Brain Stimulation Lead Designs: A Patient-Specific Simulation Study
    Öppna denna publikation i ny flik eller fönster >>Investigation into Deep Brain Stimulation Lead Designs: A Patient-Specific Simulation Study
    Visa övriga...
    2016 (Engelska)Ingår i: Brain Sciences, ISSN 2076-3425, E-ISSN 2076-3425, Vol. 6, nr 3, s. 1-16Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    New deep brain stimulation (DBS) electrode designs offer operation in voltage and current mode and capability to steer the electric field (EF). The aim of the study was to compare the EF distributions of four DBS leads at equivalent amplitudes (3 V and 3.4 mA). Finite element method (FEM) simulations (n = 38) around cylindrical contacts (leads 3389, 6148) or equivalent contact configurations (leads 6180, SureStim1) were performed using homogeneous and patient-specific (heterogeneous) brain tissue models. Steering effects of 6180 and SureStim1 were compared with symmetric stimulation fields. To make relative comparisons between simulations, an EF isolevel of 0.2 V/mm was chosen based on neuron model simulations (n = 832) applied before EF visualization and comparisons. The simulations show that the EF distribution is largely influenced by the heterogeneity of the tissue, and the operating mode. Equivalent contact configurations result in similar EF distributions. In steering configurations, larger EF volumes were achieved in current mode using equivalent amplitudes. The methodology was demonstrated in a patient-specific simulation around the zona incerta and a “virtual” ventral intermediate nucleus target. In conclusion, lead design differences are enhanced when using patient-specific tissue models and current stimulation mode.

    Ort, förlag, år, upplaga, sidor
    MDPI, 2016
    Nyckelord
    deep brain stimulation (DBS), steering, patient-specific, electric field, finite element method, neuron model, brain model, zona incerta (ZI), electrode design
    Nationell ämneskategori
    Medicinteknik
    Identifikatorer
    urn:nbn:se:liu:diva-131863 (URN)10.3390/brainsci6030039 (DOI)27618109 (PubMedID)
    Tillgänglig från: 2016-10-11 Skapad: 2016-10-11 Senast uppdaterad: 2019-11-11Bibliografiskt granskad
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    The Physical Axon: Modeling, Simulation and Electrode Evaluation
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    presentationsbild
  • 108.
    Latorre, Malcolm
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Munger, Rejean
    Ottawa Hospital Research Institute, Ottawa, ON, Canada + Dept. of Physics, University of Ottawa, ON, Canada.
    Chan, Adrian
    Linköpings universitet, Tekniska högskolan.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    The Paxon: An Electro-physical Model of a Myelinated Exon (poster)2010Konferensbidrag (Refereegranskat)
  • 109.
    Leandersson, Mats
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Hörselscreening via det publika telefonnätet: Utveckling och validering av testapplikation2010Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    En stor del av befolkningen har en hörselnedsättning men långt ifrån alla som skulle kunna dra nytta av hörselhjälpmedel söker vård i tid. Det finns ett behov av att kunna göra ett snabbt och enkelt screening-test hemifrån och i flera andra europeiska länder har det för det ändamålet tagits fram telefon- och Internetbaserade hörseltest av tresiffertyp. 

    Dessa tester spelar upp tre inlästa siffror samtidigt som ett störande brus-ljud och en adaptiv metod används för att automatiskt uppskatta testpersonens genomsnittliga, uppfattbara signal-brus-förhållande. Studier har visat att förmågan att urskilja tal i brus försämras för personer med hörselnedsättning och att den absoluta uppspelningsvolymen inte spelar väsentlig roll så länge ljudet är klart hörbart. 

    Ett svenskt talmaterial för ett sådant test har tagits fram inom EU-projektet HearCom. Syftet med examensarbetet var att implementera och validera en funktionell och prisvärd lösning i samarbete med en aktör inom telekommunikationsbranschen. 

    Efter en upphandlingsprocess valdes ett Linux-baserat system med den öppna telefonserver-programvaran Asterisk. En normalstudie genomfördes där resultaten pekar på att det utvecklade testet är jämförbart med liknande test i andra länder. Telefontestet jämfördes även med en befintlig Internetversion och båda testerna utvärderades med avseende på användbarhet. Vissa förbättringsåtgärder har föreslagits för testerna. 

    Rapporten tar också upp förutsättningar för en relevant gränssättning av testerna samt de återstående stegen till en färdig talsvarstjänst som allmänheten kan ha nytta av.

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    FULLTEXT01
  • 110.
    Leinhard, Olof Dahlqvist
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Hälsouniversitetet.
    Johansson, Andreas
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Rydell, Joakim
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Smedby, Örjan
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping.
    Nystöm, Fredrik
    Linköpings universitet, Institutionen för medicin och hälsa, Internmedicin. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Lundberg, Peter
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping.
    Borga, Magnus
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Tekniska högskolan.
    Quantitative Abdominal Fat Estimation Using MRI2008Ingår i: Proceedings - International Conference on Pattern Recognition, IEEE Computer Society, 2008, s. 1-4Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper introduces a new method for automaticquantification of subcutaneous, visceral and nonvisceralinternal fat from MR-images acquired usingthe two point Dixon technique in the abdominal region.The method includes (1) a three dimensionalphase unwrapping to provide water and fat images, (2)an image intensity inhomogeneity correction, and (3) amorphon based registration and segmentation of thetissue. This is followed by an integration of the correctedfat images within the different fat compartmentsthat avoids the partial volume effects associated withtraditional fat segmentation methods. The method wastested on 18 subjects before and after a period of fastfoodhyper-alimentation showing high stability andperformance in all analysis steps.

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    FULLTEXT01
  • 111.
    Lind, Leili
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Berglund, Aseel
    Saab Aerosystems, Linköping.
    Berglund, Erik
    Linköpings universitet, Institutionen för datavetenskap, MDALAB - Human Computer Interfaces. Linköpings universitet, Tekniska högskolan.
    Bång, Magnus
    Linköpings universitet, Institutionen för datavetenskap, MDALAB - Human Computer Interfaces. Linköpings universitet, Tekniska högskolan.
    Hägglund, Sture
    Linköpings universitet, Institutionen för datavetenskap, MDALAB - Human Computer Interfaces. Linköpings universitet, Tekniska högskolan.
    Effortless data capture for ambient e-services with digital pen and paper technology2010Ingår i: Designing Solution-Based Ubiquitous and Pervasive Computing: New Issues and Trends / [ed] Fransisco Milton Mendes Neto, Pedro Fernandes Ribeiro Neto, Information Science Publishing/IGI Global , 2010, s. 24-43Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    In order to counteract the digital divide and to enable the society to reach all its citizens with various kinds of e-services, there is a need to develop access methods and terminal technologies suited also for groups with weak access to the Internet, not the least elderly and people needing care in their homes. In this chapter, the authors will describe technologies for using digital pen and paper as data input media for e-services and computing applications, refer a number of applications together with studies and evaluations of their usability, and finally comment upon future prospects for integrating digital pen and paper as an effortless technique for data capture, especially in order to counteract and diminish the digital divide. The use of digital pen and paper technologies is exemplified with applications demonstrating its appropriateness in home care for elderly, for free-form recording of data on paper such as maps, and as a remote control for a TV set or other electronic appliances with rich functionality in the home.

  • 112.
    Lindner, Claus
    et al.
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Mora Porta, Mireia
    Department of Endocrinology and Nutrition, Hospital Clínic, Barcelona.
    Farzam, Parisa
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Squarcia, Mattia
    Department of Endocrinology and Nutrition, Hospital Clínic, Barcelona.
    Johansson, Johannes D.
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Weigel, Udo
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Halperin, Irene
    Department of Endocrinology and Nutrition, Hospital Clínic, Barcelona.
    Hanzu, Felicia
    Department of Endocrinology and Nutrition, Hospital Clínic, Barcelona.
    Durduran, Turgut
    ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Sciences and Technology.
    Diffuse optical characterization of the human thyroid2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    The human thyroid was measured by ultrasound-guided near-infrared time-resolved spectroscopy and diffuse correlation spectroscopy characterizing the healthy thyroid and nodules allowing us to envision applications in thyroid cancer screening.

  • 113.
    Lowndes, Shannely
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Blood interference in fluorescence spectrum: Experiment, analysis and comparison with intraoperativemeasurements on brain tumor2010Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The optical touch pointer (OTP), a fluorescence spectroscopy based system, assists brain surgeons during guided brain tumor resection in patients with glioblastoma multiforme (GBM). After recording and analyzing the autofluorescence spectrum of the tissue, it is possible to distinguish malignant from healthy brain tissue. A challenge during the intraoperative measurements is the interference of blood. If it gets in contact with the laser pointer, the blood blocks the light transmission to and from the tissue. The purposes of the project were to study and categorize patterns of blood interference and to present possible solutions to avoid signal blocking by blood. To measure fluorescence and reflection two devices were used respectively, the OTP which has a spectrometer and a blue laser, and the diffused reflection spectroscopy system (DRS) which has a spectrometer and a white light source. Both operate independently from each other and are connected to a fiber optical probe. A similar scenario to the one in the operation theater was simulated in the lab. Fluorescence and diffuse reflection measurements with and without blood were realized on skin and on two different plastic fluorescent standards. The results were analyzed with the aid of MatLAB, and compared with data collected in the hospital during brain tumor resection. The highest autofluorescence of brain tissue and skin is reached at approximately 506 nm. Although skin and both plastic standards have different optical properties regarding color or rather fluorescence, all of them presented very similar curves when blood on them blocked partially or completely the light transmission. A blood layer of more than 0.1 mm thickness blocks the blue laser light. Blood absorption happens at 541 and 577 nm due to oxy-hemoglobin (HbO2) in both liquid and dried blood. When the fluorescence spectrum is available but weak, the reflection spectrum contains two dips (traces of HbO2 at 541 and 577 nm). In brain there were cases in which light absorption occurred additionally at other wavelengths than the absorption peaks of deoxyhemoglobin (Hb) and HbO2. Blood interference during the OP can be prevented if the probe rests in a saline solution after every measurement. In this way the fresh blood sticking on the probe dissolves in the solution. For dried or coagulated blood, additional manual cleansing is needed.

    Ladda ner fulltext (pdf)
    Blood interference in fluorescence spectrum – Experiment, analysis and comparison with intraoperative measurements on brain tumor
  • 114.
    Lundgren, Katarina
    Linköpings universitet, Institutionen för medicinsk teknik.
    Investigation of transmural cardiac and fiber strain in ischemic and non-ischemic tissue during diastole2006Självständigt arbete på grundnivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats
    Abstract [en]

    The cardiac wall has complex three-dimensional fiber structures and mechanical properties that enable the heart to efficiently pump the blood through the body. By studying the myocardial strains induced during diastole, information about the pumping performance of the heart and what mechanisms that are responsible for this effective blood filling, can be achieved. Two different computation methods for myocardial strain, both based on data acquired from marker technique, were compared using a theoretical cylinder model. The non-homogeneous polynomial fitting method yielded higher accuracy than a homogeneous tetrahedron method, and was further used to investigate cardiac and fiber strains at different wall depths and myocardial regions in normal and ischemic ovine hearts. Large spatial and regional variations were found, as well as alterations, conveyed by ischemic conditions, of fiber mechanisms responsible for the circumferential expansion and wall thinning during diastole.

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    FULLTEXT01
  • 115. Beställ onlineKöp publikationen >>
    Lundström, Claes
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Efficient Medical Volume Visualization: An Approach Based on Domain Knowledge2007Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Direct Volume Rendering (DVR) is a visualization technique that has proved to be a very powerful tool in many scientific visualization applications. Diagnostic medical imaging is one domain where DVR could provide clear benefits in terms of unprecedented possibilities for analysis of complex cases and highly efficient work flow for certain routine examinations. The full potential of DVR in the clinical environment has not been reached, however, primarily due to limitations in conventional DVR methods and tools.

    This thesis presents methods addressing four major challenges for DVR in clinical use. The foundation of all methods is to incorporate the domain knowledge of the medical professional in the technical solutions. The first challenge is the very large data sets routinely produced in medical imaging today. To this end a multiresolution DVR pipeline is proposed, which dynamically prioritizes data according to the actual impact in the rendered image to be reviewed. Using this prioritization the system can reduce the data requirements throughout the pipeline and provide high performance and visual quality in any environment.

    Another problem addressed is how to achieve simple yet powerful interactive tissue classification in DVR. The methods presented define additional attributes that effectively captures readily available medical knowledge. The task of tissue detection is also important to solve in order to improve efficiency and consistency of diagnostic image review. Histogram-based techniques that exploit spatial relations in the data to achieve accurate and robust tissue detection are presented in this thesis.

    The final challenge is uncertainty visualization, which is very pertinent in clinical work for patient safety reasons. An animation method has been developed that automatically conveys feasible alternative renderings. The basis of this method is a probabilistic interpretation of the visualization parameters.

    Several clinically relevant evaluations of the developed techniques have been performed demonstrating their usefulness. Although there is a clear focus on DVR and medical imaging, most of the methods provide similar benefits also for other visualization techniques and application domains.

    Delarbeten
    1. Transfer Function Based Adaptive Decompresion for Volume Rendering of Large Medical Data Sets
    Öppna denna publikation i ny flik eller fönster >>Transfer Function Based Adaptive Decompresion for Volume Rendering of Large Medical Data Sets
    2004 (Engelska)Ingår i: Proceedings of IEEE/ACM Symposium on Volume Visualization 2004, Austin, USA, IEEE , 2004, s. 25-32Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    The size of standard volumetric data sets in medical imaging is rapidly increasing causing severe performance limitations in direct volume rendering pipelines. The methods presented in this paper exploit the medical knowledge embedded in the transfer function to reduce the required bandwidth in the pipeline. Typically, medical transfer functions cause large subsets of the volume to give little or no contribution to the rendered image. Thus, parts of the volume can be represented at low resolution while retaining overall visual quality. This paper introduces the use of transfer functions at decompression time to guide a level-of-detail selection scheme. The method may be used in combination with traditional lossy or lossless compression schemes. We base our current implementation on a multi-resolution data representation using compressed wavelet transformed blocks. The presented results using the adaptive decompression demonstrate a significant reduction in the required amount of data while maintaining rendering quality. Even though the focus of this paper is medical imaging, the results are applicable to volume rendering in many other domains.

    Ort, förlag, år, upplaga, sidor
    IEEE, 2004
    Nyckelord
    Adaptive decompression, Image quality measures, Medical imaging, Multiresolution, Transfer function, Volume compression, Volume rendering, Wavelet transform
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-13943 (URN)10.1109/SVVG.2004.14 (DOI)
    Tillgänglig från: 2006-09-14 Skapad: 2006-09-14 Senast uppdaterad: 2015-09-22
    2. Extending and Simplifying Transfer Function Design in Medical Volume Rendering Using Local Histograms
    Öppna denna publikation i ny flik eller fönster >>Extending and Simplifying Transfer Function Design in Medical Volume Rendering Using Local Histograms
    2005 (Engelska)Ingår i: Proceedings EuroGraphics/IEEE Symposium on Visualization 2005, Leeds, UK, 2005, s. 263-270Konferensbidrag, Publicerat paper (Övrigt vetenskapligt)
    Abstract [en]

    Direct Volume Rendering (DVR) is known to be of diagnostic value in the analysis of medical data sets. However, its deployment in everyday clinical use has so far been limited. Two major challenges are that the current methods for Transfer Function (TF) construction are too complex and that the tissue separation abilities of the TF need to be extended. In this paper we propose the use of histogram analysis in local neighborhoods to address both these conflicting problems. To reduce TF construction difficulty, we introduce Partial Range Histograms in an automatic tissue detection scheme, which in connection with Adaptive Trapezoids enable efficient TF design. To separate tissues with overlapping intensity ranges, we propose a fuzzy classification based on local histograms as a second TF dimension. This increases the power of the TF, while retaining intuitive presentation and interaction.

    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-13944 (URN)10.2312/VisSym/EuroVis05/263-270 (DOI)
    Tillgänglig från: 2006-09-14 Skapad: 2006-09-14 Senast uppdaterad: 2015-09-22
    3. Standardized volume rendering for magnetic resonance angiography measurements in the abdominal aorta
    Öppna denna publikation i ny flik eller fönster >>Standardized volume rendering for magnetic resonance angiography measurements in the abdominal aorta
    Visa övriga...
    2006 (Engelska)Ingår i: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 47, nr 2, s. 172-178Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Purpose: To compare three methods for standardizing volume rendering technique (VRT) protocols by studying aortic diameter measurements in magnetic resonance angiography (MRA) datasets.

    Material and Methods: Datasets from 20 patients previously examined with gadolinium-enhanced MRA and with digital subtraction angiography (DSA) for abdominal aortic aneurysm were retrospectively evaluated by three independent readers. The MRA datasets were viewed using VRT with three different standardized transfer functions: the percentile method (Pc-VRT), the maximum-likelihood method (ML-VRT), and the partial range histogram method (PRH-VRT). The aortic diameters obtained with these three methods were compared with freely chosen VRT parameters (F-VRT) and with maximum intensity projection (MIP) concerning inter-reader variability and agreement with the reference method DSA.

    Results: F-VRT parameters and PRH-VRT gave significantly higher diameter values than DSA, whereas Pc-VRT gave significantly lower values than DSA. The highest interobserver variability was found for F-VRT parameters and MIP, and the lowest for Pc-VRT and PRH-VRT. All standardized VRT methods were significantly superior to both MIP and F-VRT in this respect. The agreement with DSA was best for PRH-VRT, which was the only method with a mean error below 1 mm and which also had the narrowest limits of agreement (95% of cases between 2.1 mm below and 3.1 mm above DSA).

    Conclusion: All the standardized VRT methods compare favorably with MIP and VRT with freely selected parameters as regards interobserver variability. The partial range histogram method, although systematically overestimating vessel diameters, gives results closest to those of DSA.

    Nyckelord
    Abdominal aortic aneurysm (AAA); angiography; magnetic resonance angiography (MRA); maximum intensity projection (MIP); volume rendering technique (VRT); user dependence
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-14591 (URN)10.1080/02841850500445298 (DOI)000236669500010 ()
    Tillgänglig från: 2007-08-24 Skapad: 2007-08-24 Senast uppdaterad: 2017-12-13Bibliografiskt granskad
    4. Multiresolution Interblock Interpolation in Direct Volume Rendering
    Öppna denna publikation i ny flik eller fönster >>Multiresolution Interblock Interpolation in Direct Volume Rendering
    2006 (Engelska)Ingår i: Proceedings of Eurographics/IEEE Symposium on Visualization 2006, Lisbon, Portugal, 2006, s. 259-266Konferensbidrag, Publicerat paper (Övrigt vetenskapligt)
    Abstract [en]

    We present a direct interblock interpolation technique that enables direct volume rendering of blocked, multiresolution volumes. The proposed method smoothly interpolates between blocks of arbitrary block-wise level-of-detail (LOD) without sample replication or padding. This permits extreme changes in resolution across block boundaries and removes the interblock dependency for the LOD creation process. In addition the full data reduction from the LOD selection can be maintained throughout the rendering pipeline. Our rendering pipeline employs a flat block subdivision followed by a transfer function based adaptive LOD scheme. We demonstrate the effectiveness of our method by rendering volumes of the order of gigabytes using consumer graphics cards on desktop PC systems.

    Nyckelord
    Viewing algorithms; Image Processing; Computer Vision
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-13945 (URN)10.2312/VisSym/EuroVis06/259-266 (DOI)
    Tillgänglig från: 2006-09-14 Skapad: 2006-09-14 Senast uppdaterad: 2015-09-22
    5. The alpha-histogram: Using Spatial Coherence to Enhance Histograms and Transfer Function Design
    Öppna denna publikation i ny flik eller fönster >>The alpha-histogram: Using Spatial Coherence to Enhance Histograms and Transfer Function Design
    Visa övriga...
    2006 (Engelska)Ingår i: Proceedings Eurographics/IEEE Symposium on Visualization 2006, Lisbon, Portugal, 2006, s. 227-234Konferensbidrag, Publicerat paper (Övrigt vetenskapligt)
    Abstract [en]

    The high complexity of Transfer Function (TF) design is a major obstacle to widespread routine use of Direct Volume Rendering, particularly in the case of medical imaging. Both manual and automatic TF design schemes would benefit greatly from a fast and simple method for detection of tissue value ranges. To this end, we introduce the a-histogram, an enhancement that amplifies ranges corresponding to spatially coherent materials. The properties of the a-histogram have been explored for synthetic data sets and then successfully used to detect vessels in 20 Magnetic Resonance angiographies, proving the potential of this approach as a fast and simple technique for histogram enhancement in general and for TF construction in particular.

    Nyckelord
    Picture/Image Generation; Methodology and Techniques; Three-Dimensional Graphics and Realism
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-13946 (URN)10.2312/VisSym/EuroVis06/227-234 (DOI)
    Tillgänglig från: 2006-09-14 Skapad: 2006-09-14 Senast uppdaterad: 2015-09-22
    6. Multi-Dimensional Transfer Function Design Using Sorted Histograms
    Öppna denna publikation i ny flik eller fönster >>Multi-Dimensional Transfer Function Design Using Sorted Histograms
    2006 (Engelska)Ingår i: Proceedings Eurographics/IEEE International Workshop on Volume Graphics 2006, Boston, USA, 2006, s. 1-8Konferensbidrag, Publicerat paper (Övrigt vetenskapligt)
    Abstract [en]

    Multi-dimensional Transfer Functions (MDTFs) are increasingly used in volume rendering to produce high quality visualizations of complex data sets. A major factor limiting the use of MDTFs is that the available design tools have not been simple enough to reach wide usage outside of the research context, for instance in clinical medical imaging. In this paper we address this problem by defining an MDTF design concept based on improved histogram display and interaction in an exploratory process. To this end we propose sorted histograms, 2D histograms that retain the intuitive appearance of a traditional 1D histogram while conveying a second attribute. We deploy the histograms in medical visualizations using data attributes capturing domain knowledge e.g. in terms of homogeneity and typical surrounding of tissues. The resulting renderings demonstrate that the proposed concept supports a vast number of visualization possibilities based on multi-dimensional attribute data.

    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-13948 (URN)10.2312/VG/VG06/001-008 (DOI)
    Tillgänglig från: 2006-09-14 Skapad: 2006-09-14 Senast uppdaterad: 2015-09-22
    7. Local histograms for design of Transfer Functions in Direct Volume Rendering
    Öppna denna publikation i ny flik eller fönster >>Local histograms for design of Transfer Functions in Direct Volume Rendering
    2006 (Engelska)Ingår i: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 12, nr 6, s. 1570-1579Artikel i tidskrift (Övrigt vetenskapligt) Published
    Abstract [en]

    Direct Volume Rendering (DVR) is of increasing diagnostic value in the analysis of data sets captured using the latest medical imaging modalities. The deployment of DVR in everyday clinical work, however, has so far been limited. One contributing factor is that current Transfer Function (TF) models can encode only a small fraction of the user's domain knowledge. In this paper, we use histograms of local neighborhoods to capture tissue characteristics. This allows domain knowledge on spatial relations in the data set to be integrated into the TF. As a first example, we introduce Partial Range Histograms in an automatic tissue detection scheme and present its effectiveness in a clinical evaluation. We then use local histogram analysis to perform a classification where the tissue-type certainty is treated as a second TF dimension. The result is an enhanced rendering where tissues with overlapping intensity ranges can be discerned without requiring the user to explicitly define a complex, multidimensional TF.

    Nyckelord
    Volume visualization, transfer function, medical imaging, classification, partial range histogram
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-13949 (URN)10.1109/TVCG.2006.100 (DOI)
    Tillgänglig från: 2006-09-14 Skapad: 2006-09-14 Senast uppdaterad: 2017-12-13
    8. Full Body Virtual Autopsies Using A State-of-the-art Volume Rendering Pipeline
    Öppna denna publikation i ny flik eller fönster >>Full Body Virtual Autopsies Using A State-of-the-art Volume Rendering Pipeline
    Visa övriga...
    2006 (Engelska)Ingår i: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 12, nr 5, s. 869-876Artikel i tidskrift (Övrigt vetenskapligt) Published
    Abstract [en]

    This paper presents a procedure for virtual autopsies based on interactive 3D visualizations of large scale, high resolutiondata from CT-scans of human cadavers. The procedure is described using examples from forensic medicine and the added valueand future potential of virtual autopsies is shown from a medical and forensic perspective. Based on the technical demands ofthe procedure state-of-the-art volume rendering techniques are applied and refined to enable real-time, full body virtual autopsiesinvolving gigabyte sized data on standard GPUs. The techniques applied include transfer function based data reduction using levelof-detail selection and multi-resolution rendering techniques. The paper also describes a data management component for large,out-of-core data sets and an extension to the GPU-based raycaster for efficient dual TF rendering. Detailed benchmarks of thepipeline are presented using data sets from forensic cases.

    Nyckelord
    Forensics, autopsies, medical visualization, volume rendering, large scale data
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-13950 (URN)10.1109/TVCG.2006.146 (DOI)000241383300028 ()
    Tillgänglig från: 2006-09-14 Skapad: 2006-09-14 Senast uppdaterad: 2017-12-13
    9. Uncertainty Visualization in Medical Volume Rendering Using Probabilistic Animation
    Öppna denna publikation i ny flik eller fönster >>Uncertainty Visualization in Medical Volume Rendering Using Probabilistic Animation
    2007 (Engelska)Ingår i: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 13, nr 6, s. 1648-1655Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Direct volume rendering has proved to be an effective visualization method for medical data sets and has reached wide-spread clinical use. The diagnostic exploration, in essence, corresponds to a tissue classification task, which is often complex and time-consuming. Moreover, a major problem is the lack of information on the uncertainty of the classification, which can have dramatic consequences for the diagnosis. In this paper this problem is addressed by proposing animation methods to convey uncertainty in the rendering. The foundation is a probabilistic Transfer Function model which allows for direct user interaction with the classification. The rendering is animated by sampling the probability domain over time, which results in varying appearance for uncertain regions. A particularly promising application of this technique is a "sensitivity lens" applied to focus regions in the data set. The methods have been evaluated by radiologists in a study simulating the clinical task of stenosis assessment, in which the animation technique is shown to outperform traditional rendering in terms of assessment accuracy.

    Nyckelord
    uncertainty, medical visualization, probability, transfer function, volume rendering
    Nationell ämneskategori
    Medicinsk laboratorie- och mätteknik
    Identifikatorer
    urn:nbn:se:liu:diva-14597 (URN)10.1109/TVCG.2007.70518 (DOI)000250401100076 ()
    Tillgänglig från: 2007-08-24 Skapad: 2007-08-24 Senast uppdaterad: 2017-12-13
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  • 116.
    Lundström, Claes
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Ljung, Patric
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Ynnerman, Anders
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Persson, Anders
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Uncertainty Visualization in Medical Volume Rendering Using Probabilistic Animation2007Ingår i: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 13, nr 6, s. 1648-1655Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Direct volume rendering has proved to be an effective visualization method for medical data sets and has reached wide-spread clinical use. The diagnostic exploration, in essence, corresponds to a tissue classification task, which is often complex and time-consuming. Moreover, a major problem is the lack of information on the uncertainty of the classification, which can have dramatic consequences for the diagnosis. In this paper this problem is addressed by proposing animation methods to convey uncertainty in the rendering. The foundation is a probabilistic Transfer Function model which allows for direct user interaction with the classification. The rendering is animated by sampling the probability domain over time, which results in varying appearance for uncertain regions. A particularly promising application of this technique is a "sensitivity lens" applied to focus regions in the data set. The methods have been evaluated by radiologists in a study simulating the clinical task of stenosis assessment, in which the animation technique is shown to outperform traditional rendering in terms of assessment accuracy.

  • 117.
    Läthén, Gunnar
    et al.
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för teknik och naturvetenskap, Digitala Medier. Linköpings universitet, Tekniska högskolan.
    Andersson, Thord
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Lenz, Reiner
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för teknik och naturvetenskap, Digitala Medier. Linköpings universitet, Tekniska högskolan.
    Borga, Magnus
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Momentum Based Optimization Methods for Level Set Segmentation2009Ingår i: Momentum Based Optimization Methods for Level Set Segmentation: Second International Conference, SSVM 2009, Voss, Norway, June 1-5, 2009. Proceedings / [ed] Gerhard Goos, Juris Hartmanis, and Jan van Leeuwen, Berlin: Springer Berlin/Heidelberg, 2009, s. 124-136Konferensbidrag (Refereegranskat)
    Abstract [en]

    Segmentation of images is often posed as a variational problem. As such, it is solved by formulating an energy functional depending on a contour and other image derived terms. The solution of the segmentation problem is the contour which extremizes this functional. The standard way of solving this optimization problem is by gradient descent search in the solution space, which typically suffers from many unwanted local optima and poor convergence. Classically, these problems have been circumvented by modifying the energy functional. In contrast, the focus of this paper is on alternative methods for optimization. Inspired by ideas from the machine learning community, we propose segmentation based on gradient descent with momentum. Our results show that typical models hampered by local optima solutions can be further improved by this approach. We illustrate the performance improvements using the level set framework.

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    FULLTEXT02
  • 118.
    Läthén, Gunnar
    et al.
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för teknik och naturvetenskap, Digitala Medier. Linköpings universitet, Tekniska högskolan.
    Jonasson, Jimmy
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Borga, Magnus
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Tekniska högskolan.
    Blood vessel segmentation using multi-scale quadrature filtering2010Ingår i: Pattern Recognition Letters, ISSN 0167-8655, E-ISSN 1872-7344, Vol. 31, nr 8, s. 762-767Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The segmentation of blood vessels is a common problem in medical imagingand various applications are found in diagnostics, surgical planning, trainingand more. Among many dierent techniques, the use of multiple scales andline detectors is a popular approach. However, the typical line lters usedare sensitive to intensity variations and do not target the detection of vesselwalls explicitly. In this article, we combine both line and edge detection usingquadrature lters across multiple scales. The lter result gives well denedvessels as linear structures, while distinct edges facilitate a robust segmentation.We apply the lter output to energy optimization techniques for segmentationand show promising results in 2D and 3D to illustrate the behavior of ourmethod. The conference version of this article received the best paper award inthe bioinformatics and biomedical applications track at ICPR 2008.

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  • 119.
    Läthén, Gunnar
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Digitala Medier. Linköpings universitet, Tekniska högskolan.
    Jonasson, Jimmy
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Borga, Magnus
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Tekniska högskolan.
    Phase Based Level Set Segmentation of Blood Vessels2008Ingår i: Proceedings of 19th International Conference on Pattern Recognition, IEEE Computer Society , 2008, s. 1-4Konferensbidrag (Refereegranskat)
    Abstract [en]

    The segmentation and analysis of blood vessels hasreceived much attention in the research community. Theresults aid numerous applications for diagnosis andtreatment of vascular diseases. Here we use level setpropagation with local phase information to capture theboundaries of vessels. The basic notion is that localphase, extracted using quadrature filters, allows us todistinguish between lines and edges in an image. Notingthat vessels appear either as lines or edge pairs, weintegrate multiple scales and capture information aboutvessels of varying width. The outcome is a “global”phase which can be used to drive a contour robustly towardsthe vessel edges. We show promising results in2D and 3D. Comparison with a related method givessimilar or even better results and at a computationalcost several orders of magnitude less. Even with verysparse initializations, our method captures a large portionof the vessel tree.

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    FULLTEXT01
  • 120.
    Magnusson, Maria
    et al.
    Linköpings universitet, Institutionen för systemteknik, Bildbehandling. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Dahlqvist Leinhard, Olof
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Brynolfsson, Patrik
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Thyr, Per
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Lundberg, Peter
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Bildmedicinskt centrum, Röntgenkliniken i Linköping. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    3D Magnetic Resonance Imaging of the Human Brain - Novel Radial Sampling, Filtering and Reconstruction2010Ingår i: Proc of the 12th IASTED International Conference on Signal and Image Processing (SIP 2010), August 23 - 25, 2010, Lahaina, Maui, USA / [ed] B. Flinchbaugh, Calgary, AB, Canada: ACTA Press, 2010, s. Track: 710-042-(8 pages)Konferensbidrag (Refereegranskat)
    Abstract [en]

    We have suggested a novel method PRESTO-CAN including radial sampling, filtering and reconstruction of k-space data for 3D-plus-time resolved MRI. The angular increment of the profiles was based on the golden ratio, but the number of angular positions N was locked to be a prime number which guaranteed fix angle positions.The time resolution increased dramatically when the pro-files were partly removed from the k-space using the hourglass filter.We aim for utilizing the MRI-data for fMRI, where the echo times are long, TE ≈ 37-40 ms. This will result in field inhomogeneities and phase variations in the reconstructed images. Therefore, a new calibration and correction procedure was developed. We show that we are able to reconstruct images of the human brain with an image quality in line with what can be obtained by conventional Cartesian sampling.The pulse sequence for PRESTO-CAN was implemented by modifying an existing PRESTO sequence for Cartesian sampling. The effort involved was relatively small and a great advantage will be that we are able to use standard procedures for speeding up data acquisition, i.e. parallel imaging with SENSE.

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  • 121. Beställ onlineKöp publikationen >>
    Mirdell, Robin
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för Kirurgi, Ortopedi och Onkologi. Linköpings universitet, Medicinska fakulteten.
    Blood Flow Dynamics in Burns2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Objectives:

    Burns of intermediate thickness are hard to evaluate clinically. This often leads to unnecessary delays of up to 14 days before a surgical decision can be made. To counter this, several objective methods have been developed to determine the healing potential of the wound. Over the years, measurement of perfusion has proven to be the most successful method for evaluation of healing potential. Laser Doppler imaging (LDI) is currently the most used method and can determine surgical need 2 days after injury with an accuracy >90%.  

    There are however emerging techniques like laser speckle contrast imaging (LSCI), which also measure perfusion. LSCI have several advantages over LDI and is easier to use. LSCI can also investigate aspects of the microcirculation, previously not possible with LDI. The aim of this thesis was to investigate LSCI’s ability to evaluate surgical need in burns of indeterminate partial-thickness.  

    The first objective was to investigate the dynamics of perfusion the first 14 days after injury. The purpose was to find the optimal time-window for perfusion measurements. The next goal was to determine the accuracy of different perfusion cut-offs. In this second study, the benefit of a subsequent measurement was also investigated. After this, interobserver variation between different profession groups was studied. Both the agreement of perfusion measurements and observer assessments were evaluated. Finally, cardiac vasomotion in combination with perfusion (pulsatility) was investigated as a method to determine surgical need <48 hours after injury.  

    Methods:

    Perfusion was measured in a total of 77 patients at the Department of Plastic Surgery, Hand Surgery and Burns at Linköping University Hospital, Sweden. Most of these patients were children and the most common type of burn was scalds. A laser speckle contrast imager (PeriCam PSI System, Perimed AB, Järfälla, Sweden) was used to measure perfusion.  

    Results:  

    In the first paper we showed a clear relation between perfusion dynamics and the healing potential of the wound. The changes in perfusion were largest the first 5 days after injury, why this time interval was selected for subsequent papers. Perfusion measurements done day 3-4 after injury could predict surgical need with a sensitivity of 100% (95% CI: 83.9-100%) and a specificity of 90.4% (95% CI: 83.8-94.9%). If two measurements were used, <24 hours and 3-4 days after injury, the accuracy was 100%. Furthermore, we found that different observers could consistently predict perfusion, while there was a large variation in their clinical assessments. This was not improved by extensive burn experience. Finally, pulsatility could be used to predict surgical need the same day as the injury occurred with a sensitivity of 100% (95% CI: 88.1-100%) and a specificity of 98.8% (95% CI: 95.7- 99.9%).  

    Conclusions:  

    LSCI is a promising method for evaluation of burns and provides several benefits over LDI. The surgical need of burns can be determined mere hours after injury when pulsatility is measured. However, the benefits of early scald diagnostics in children with LSCI need to be evaluated in a prospective study before the method is ready for routine clinical use.

    Delarbeten
    1. Microvascular blood flow in scalds in children and its relation to duration of wound healing: A study using laser speckle contrast imaging
    Öppna denna publikation i ny flik eller fönster >>Microvascular blood flow in scalds in children and its relation to duration of wound healing: A study using laser speckle contrast imaging
    Visa övriga...
    2016 (Engelska)Ingår i: Burns, ISSN 0305-4179, E-ISSN 1879-1409, Vol. 42, nr 3, s. 648-654Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Background: Microvascular perfusion changes in scalds in children during the first weeks after injury is related to the outcome of healing, and measurements of perfusion, based on laser Doppler imaging, have been used successfully to predict the need for excision and grafting. However, the day-to-day changes in perfusion during the first weeks after injury have not to our knowledge been studied in detail. The aim of this study, based on a conservative treatment model where excision and grafting decisions were delayed to day 14 after injury, was to measure changes in perfusion in scalds using laser speckle contrast imaging (LSCI) during the first three weeks after injury. Methods: We measured perfusion with LSCI in 34 patients at regular intervals between 6 h after injury until complete reepithelialization or surgery. Duration of healing was defined as the time to complete reepithelialization. Results: Less perfusion, between 6 and 96 h after injury, was associated with longer duration of healing with the strongest association occurring between 72 and 96 h. Burns that healed within 14 days had relatively high initial perfusion, followed by a peak and subsequent slow decrease. Both the maximum perfusion and the time-to-peak were dependent on the severity of the burn. Burns that needed excision and grafting had less initial perfusion and a gradual reduction over time. Conclusion: The perfusion in scalds in children shows characteristic patterns during the first weeks after injury depending on the duration of wound healing, the greatest difference between wounds of different severity being on the 4th day. Perfusion should therefore preferably be measured on the fourth day if it is to be used in the assessment of burn depth. (c) 2015 Elsevier Ltd and ISBI. All rights reserved.

    Ort, förlag, år, upplaga, sidor
    ELSEVIER SCI LTD, 2016
    Nyckelord
    Scalds; Burns; Perfusion; Laser speckle contrast imaging
    Nationell ämneskategori
    Anestesi och intensivvård
    Identifikatorer
    urn:nbn:se:liu:diva-129497 (URN)10.1016/j.burns.2015.12.005 (DOI)000376507500023 ()26810445 (PubMedID)
    Tillgänglig från: 2016-06-20 Skapad: 2016-06-20 Senast uppdaterad: 2019-11-25
    2. Accuracy of laser speckle contrast imaging in the assessment of pediatric scald wounds
    Öppna denna publikation i ny flik eller fönster >>Accuracy of laser speckle contrast imaging in the assessment of pediatric scald wounds
    2018 (Engelska)Ingår i: Burns, ISSN 0305-4179, E-ISSN 1879-1409, Vol. 44, nr 1, s. 90-98Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Background: Changes in microvascular perfusion in scalds in children during the first four days, measured with laser speckle contrast imaging (LSCI), are related to the time to healing and need for surgical intervention. The aim of this study was to determine the accuracy (sensitivity and specificity) of LSCI on different days after injury in the prediction of healing outcome and if the accuracy can be improved by combining an early and a late measurement. Also, the accuracy of LSCI was compared with that of clinical assessment. Methods: Perfusion was measured between 0-24h and between 72-96h using LSCI in 45 children with scalds. On the same occasions, burn surgeons assessed the burns as healing amp;lt; 14days or healing amp;gt; 14days/surgery. Receiver operating characteristic (ROC) curves were constructed for the early and late measurement and for the double measurement (DM) using two different methods. Results: Sensitivity and specificity were 92.3% (95% CI: 64.0-99.8%) and 78.3% (95% CI: 69.985.3%) between 0-24h, 100% (95% CI: 84.6-100%) and 90.4% (95% CI: 83.8-94.9%) between 72-96h, and was 100% (95% CI: 59.0-100%) and 100% (95% CI: 95.1-100%) when combining the two measurements into a modified perfusion trend. Clinical assessment had an accuracy of 67%, Cohens k=0.23. Conclusion: The perfusion in scalds between 72-96h after injury, as measured using LSCI, is highly predictive of healing outcome in scalds when measured. The predictive value can be further improved by incorporating an early perfusion measurement within 24h after injury. (C) 2017 Elsevier Ltd and ISBI. All rights reserved.

    Ort, förlag, år, upplaga, sidor
    ELSEVIER SCI LTD, 2018
    Nyckelord
    Burn severity; Burn assessment; Scalds; Laser speckle contrast imaging
    Nationell ämneskategori
    Anestesi och intensivvård
    Identifikatorer
    urn:nbn:se:liu:diva-144874 (URN)10.1016/j.burns.2017.06.010 (DOI)000422665600012 ()28797578 (PubMedID)
    Tillgänglig från: 2018-02-09 Skapad: 2018-02-09 Senast uppdaterad: 2019-11-25
    3. Interobserver reliability of laser speckle contrast imaging in the assessment of burns
    Öppna denna publikation i ny flik eller fönster >>Interobserver reliability of laser speckle contrast imaging in the assessment of burns
    2019 (Engelska)Ingår i: Burns, ISSN 0305-4179, E-ISSN 1879-1409, Vol. 45, nr 6, s. 1325-1335Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Objectives: Laser speckle contrast imaging (LSCI) is an emerging technique for the assessment of burns in humans and interobserver differences have not been studied. The aim of this study was to compare assessments of perfusion images by different professional groups regarding (i) perfusion values and (ii) burn depth assessment. Methods: Twelve observers without LSCI experience were included. The observers were evenly recruited from three professional groups: plastic surgeons with experience in assessing burns, nurses with experience in treating burns, and junior doctors with limited experience of burns. Ten cases were included. Each case consisted of one digital photo of the burn with a pre-marked region of interest (ROI) and two unmarked perfusion images of the same area. The first and the second perfusion image was from 24h and 72-96h after injury, respectively. The perfusion values from both perfusion images were used to generate a LSCI recommendation based on the perfusion trend (the derivative between the two perfusion values). As a last step, each observer was asked to estimate the burn depth using their clinical experience and all available information. Intraclass correlation (ICC) was calculated between the different professional groups and among all observers. Results: Perfusion values and perfusion trends between all observers had an ICC of 0.96 (95% CI 0.91-0.99). Burn depth assessment by all observers yielded an ICC of 0.53 (95% CI: 0.31-0.80) and an accuracy of 0.53 (weighted kappa). LSCI recommendations generated by all observers had an ICC of 0.95 (95% CI: 0.90-0.99). Conclusion: Observers can reliably identify the same ROI, which results in observer-independent perfusion measurements, irrespective of burn experience. Extensive burn experience did not further improve burn depth assessment. The LSCI recommendation was more accurate in all professional groups. Introducing LSCI measurements would be likely improve early assessment of burns. (C) 2019 Elsevier Ltd and ISBI. All rights reserved.

    Ort, förlag, år, upplaga, sidor
    ELSEVIER SCI LTD, 2019
    Nyckelord
    Burn severity; Burn assessment; Scalds; Laser speckle contrast imaging; Interobserver
    Nationell ämneskategori
    Anestesi och intensivvård
    Identifikatorer
    urn:nbn:se:liu:diva-160407 (URN)10.1016/j.burns.2019.01.011 (DOI)000483339500008 ()31230800 (PubMedID)
    Tillgänglig från: 2019-09-23 Skapad: 2019-09-23 Senast uppdaterad: 2020-05-02
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  • 122.
    Mirdell, Robin
    et al.
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för Kirurgi, Ortopedi och Onkologi. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Sinnescentrum, Hand- och plastikkirurgiska kliniken US.
    Lemstra-Idsardi, Aukje Nienke
    Univ Twente, Netherlands.
    Farnebo, Simon
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för Kirurgi, Ortopedi och Onkologi. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Sinnescentrum, Hand- och plastikkirurgiska kliniken US.
    Tesselaar, Erik
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för Kirurgi, Ortopedi och Onkologi. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Diagnostikcentrum, Medicinsk strålningsfysik. Linköpings universitet, Institutionen för medicin och hälsa.
    The presence of synchronized perfusion dips in the microcirculation of the resting nail bed2019Ingår i: Microvascular Research, ISSN 0026-2862, E-ISSN 1095-9319, Vol. 121, s. 71-81Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objectives: Laser speckle contrast imaging (LSCI) has seen limited use in the study of perfusion dynamics such as vasomotion. The aim of this study was to investigate the effects of a prolonged seated position on perfusion dynamics in the nail bed using LSCI. Methods: Perfusion was recorded in digits II to IV bilaterally for 20 min during two separate sessions in ten healthy volunteers. The acclimatization period was 5 min for the 1st session and 20 min for the 2nd. Perfusion variability and the presence of recurring perfusion dips were analyzed. A digital nerve block was done to verify suspected nervous origin of phenomenon. Results: Synchronized phases of vasoconstriction were observed in all subjects with perfusion dips in all digits bilaterally and simultaneously. Application of a digital nerve block abolished perfusion dips. The frequency of this phenomenon increased by 25.0% (95% CI: 1.6 to 49.2%) in the left-hand digits after a prolonged seated position. Perfusion variability increased by 11.6% (95% CI: 2.6 to 20.3%) in the digits of the left hand. Perfusion changes in right-hand digits did not significantly increase. During the 1st session, temperature increased by 2.7 degrees C (1.1 to 4.2) while it decreased by 1.3 degrees C (0.2 to 2.4) during the 2nd session. Conclusion: The observed perfusion dips are of a centrally mediated nervous origin but are also affected by local factors. They are affected by seating duration and differ between left and right hands, likely because of local micro perfusion dips. This phenomenon seems related to digital thermoregulation.

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  • 123.
    Naslund, Erik
    et al.
    Uppsala Univ, Sweden; Gavle Cent Hosp, Sweden.
    Lindberg, Lars-Göran
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Lund, Irene
    Karolinska Inst, Sweden.
    Naslund-Koch, Lui
    Bornholm Hosp, Denmark.
    Larsson, Agneta
    Uppsala Univ, Sweden; Karolinska Inst, Sweden.
    Frithiof, Robert
    Uppsala Univ, Sweden.
    Measuring arterial oxygen saturation from an intraosseous photoplethysmographic signal derived from the sternum2020Ingår i: Journal of clinical monitoring and computing, ISSN 1387-1307, E-ISSN 1573-2614, Vol. 34, nr 1, s. 55-62Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Photoplethysmography performed on the peripheral extremities or the earlobes cannot always provide sufficiently rapid and accurate calculation of arterial oxygen saturation. The purpose of this study was to evaluate a novel photoplethysmography prototype to be fixed over the sternum. Our hypotheses were that arterial oxygen saturation can be determined from an intraosseous photoplethysmography signal from the sternum and that such monitoring detects hypoxemia faster than pulse oximetry at standard sites. Sixteen healthy male volunteers were subjected to incremental hypoxemia using different gas mixtures with decreasing oxygen content. The sternal probe was calibrated using arterial haemoglobin CO-oximetry (SaO2%). Sternal probe readings (SRHO2%) were then compared to SaO2% at various degrees of hypoxia. The time to detect hypoxemia was compared to measurements from standard finger and ear pulse oximeters. A significant association from individual regression between SRHO2% and SaO2% was found (r(2) 0.97), Spearman R ranged between 0.71 and 0.92 for the different inhaled gas mixtures. Limits of agreement according to Bland-Altman plots had a increased interval with decreasing arterial oxygen saturation. The sternal probe detected hypoxemia 28.7 s faster than a finger probe (95% CI 20.0-37.4 s, p amp;lt; 0.001) and 6.6 s faster than an ear probe (95% CI 5.3-8.7 s, p amp;lt; 0.001). In an experimental setting, arterial oxygen saturation could be determined using the photoplethysmography signal obtained from sternal blood flow after calibration with CO-oximetry. This method detected hypoxemia significantly faster than pulse oximetry performed on the finger or the ear.

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  • 124.
    Nguyen, Tho
    Linköpings universitet, Institutionen för medicinsk teknik.
    ZigBee-teknikens möjligheter att trådlöst överföra EKG-signaler2007Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats
    Abstract [en]

    In many clinical applications, it is desirable to transmit sensor information wireless. In earlier research, investigation transmit ECG signal using Bluetooth, was performed. However, when Bluetooth has some drawbacks it is of interest to investigate alternative methods, one such method is ZigBee. Bluetooth has higher data rate speed (1Mbps) than ZigBee (250kbps). However, Bluetooth consumes more power. ZigBee uses in applications where low power consumption is important compared to high data rate. For industrial purposes, ZigBee is used in sensors and control unit technology. For medical treatment ZigBee can be used for patient monitoring.

    The aim of this work is to investigate if it is possible to wireless transmit an ECG signal with ZigBee-technology.

    The result shows that an ECG signal can be transmitted by using ZigBee. Since ZigBee is designed for low power consumption, the Zigbee-module must be set in passive mode in most of the time.

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  • 125.
    Nilsson, Gert
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Salerud, Göran
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Strömberg, Tomas
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Larsson, M.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Laser Doppler Perfusion Monitoring and Imaging2003Ingår i: Biomedical Photonics Handbook / [ed] Tuan Vo-Dinh, CRC Press , 2003, 1, s. -1872Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    A wide variety of biomedical photonic technologies have been developed recently for clinical monitoring of early disease states; molecular diagnostics and imaging of physiological parameters; molecular and genetic biomarkers; and detection of the presence of pathological organisms or biochemical species of clinical importance. However, available information on this rapidly growing field is fragmented among a variety of journals and specialized books.Now researchers and medical practitioners have an authoritative and comprehensive source for the latest research and applications in biomedical photonics. Over 150 leading scientists, engineers, and physicians discuss state-of-the-art instrumentation, methods, and protocols in the Biomedical Photonics Handbook. Editor-in-Chief Tuan Vo-Dinh and an advisory board of distinguished scientists and medical experts ensure that each of the 65 chapters represents the latest and most accurate information currently available.

  • 126.
    Nilsson, Gert
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Elektriska säkerhetsproblem i: Styrd värmedyna för kliniskt bruk1974Rapport (Övrig (populärvetenskap, debatt, mm))
  • 127.
    Nilsson, Gert
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Elektriska säkerhetsproblem II: En överblick över medicintekniska säkerhetsfrågor1974Rapport (Övrig (populärvetenskap, debatt, mm))
  • 128.
    Nilsson, Gert
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Elektriska säkerhetsproblem III: Referenslista1974Rapport (Övrig (populärvetenskap, debatt, mm))
  • 129.
    Nilsson, Gunnar H.
    et al.
    Karolinska Institutetet, Sweden.
    Månsson, Jörgen
    Primary Health Care Centre Husläkarna i Kungsbacka, Sweden.
    Åhlfeldt, Hans
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Gunnarsson, Ronny
    Göteborg University, Sweden.
    Strender, Lars-Erik
    Karolinska Institutetet, Sweden.
    Patients, general practitioners, diseases and health problems in urban general practice: a cross-sectional study on electronic patient records2008Ingår i: Primary Health Care Research and Development, ISSN 1463-4236, E-ISSN 1477-1128, Vol. 9, nr 2, s. 119-125Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background Statistics from primary health care in Sweden, as well as from other Nordic countries, have been sparse. The electronic patient records (EPR) will be an increasingly important source of clinical information. The aim of this study was to investigate types of encounters, managed diseases and health problems, and characteristics of patients and general practitioners (GPs) in everyday general practice using EPR.

    Methods A multi-centre, cross-sectional database study of EPR in primary health care in Stockholm, Sweden. Twenty-six randomly selected GPs with 20 randomly selected encounters each. Main outcome measures were the number and distribution of diseases and health problems, age and gender of patients and GPs, and type of encounter.

    Results The mean age of the patients was 51.2 years, 30.2% were aged 75 years or older, and 57.5% were women. The mean number of managed problems per encounter was 1.4. The most common specific diagnoses were essential hypertension (9.3% of the encounters) and acute upper respiratory infections (8.8%). Older patients had more health problems in each encounter (P = 0.000001). GPs differed regarding the characteristics of their patients, including sex, age and number of health problems managed at each encounter. The patients of different GPs differed regarding sex, age and number of health problems managed. Female and male patients had different diagnostic panoramas and they had a tendency to encounter a GP of the same sex (odds ratio 1.5, P = 0.053).

    Conclusions We found that two diagnoses (essential hypertension and acute upper respiratory infections), four diagnostic groups, women and the elderly are predominant. Female and male patients have different diagnostic panoramas and they have a tendency to encounter a GP of the same sex. GPs differ regarding the characteristics of their patients, including sex, age and number of health problems managed at each encounter.

  • 130.
    Nordin, Teresa
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Zsigmond, Peter
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för neuro- och inflammationsvetenskap. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Sinnescentrum, Neurokirurgiska kliniken US.
    Pujol, Sonia
    Laboratory of Mathematics in Imaging, Brigham and Women's Hospital, Harvard Medical School, USA / Surgical Planning Laboratory, Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, USA.
    Westin, Carl-Fredrik
    Laboratory of Mathematics in Imaging, Brigham and Women's Hospital, Harvard Medical School, USA.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    White matter tracing combined with electric field simulation –€“ A patient-specific approach for deep brain stimulation2019Ingår i: NeuroImage: Clinical, ISSN 0353-8842, E-ISSN 2213-1582, Vol. 24, s. 1-11, artikel-id 102026Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objective

    Deep brain stimulation (DBS) in zona incerta (Zi) is used for symptom alleviation in essential tremor (ET). Zi is positioned along the dentato-rubro-thalamic tract (DRT). Electric field simulations with the finite element method (FEM) can be used for estimation of a volume where the stimulation affects the tissue by applying a fixed isolevel (VDBS). This work aims to develop a workflow for combined patient-specific electric field simulation and white matter tracing of the DRT, and to investigate the influence on the VDBS from different brain tissue models, lead design and stimulation modes. The novelty of this work lies in the combination of all these components.

    Method

    Patients with ET were implanted in Zi (lead 3389, n = 3, voltage mode; directional lead 6172, n = 1, current mode). Probabilistic reconstruction from diffusion MRI (dMRI) of the DRT (n = 8) was computed with FSL Toolbox. Brain tissue models were created for each patient (two homogenous, one heterogenous isotropic, one heterogenous anisotropic) and the respective VDBS (n = 48) calculated from the Comsol Multiphysics FEM simulations. The DRT and VDBS were visualized with 3DSlicer and superimposed on the preoperative T2 MRI, and the common volumes calculated. Dice Coefficient (DC) and level of anisotropy were used to evaluate and compare the brain models.

    Result

    Combined patient-specific tractography and electric field simulation was designed and evaluated, and all patients showed benefit from DBS. All VDBS overlapped the reconstructed DRT. Current stimulation showed prominent difference between the tissue models, where the homogenous grey matter deviated most (67 < DC < 69). Result from heterogenous isotropic and anisotropic models were similar (DC > 0.95), however the anisotropic model consistently generated larger volumes related to a greater extension of the electric field along the DBS lead. Independent of tissue model, the steering effect of the directional lead was evident and consistent.

    Conclusion

    A workflow for patient-specific electric field simulations in combination with reconstruction of DRT was successfully implemented. Accurate tissue classification is essential for electric field simulations, especially when using the current control stimulation. With an accurate targeting and tractography reconstruction, directional leads have the potential to tailor the electric field into the desired region.

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  • 131.
    Olsson, Linda
    Linköpings universitet, Institutionen för medicinsk teknik.
    Possibilities for the development of a decision support system for diagnosing heart failure2007Självständigt arbete på grundnivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats
    Abstract [en]

    Heart failure is a common disease which is difficult to diagnose. To aid physicians in diagnosing heart failure, a decision support system has been proposed. Parameters useful to the system are suggested. Some of these, such as age and gender, should be provided by the physician, and some should be derived from electro- and phonocardiographic signals.

    Various methods of signal processing, such as wavelet theory and principal components analysis, are described. Heart failure should be diagnosed based on the parameters, and so various forms of decision support systems, such as neural networks and support vector machines, are described. The methods of signal processing and classification are discussed and suggestions on how to develop the system are made.

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  • 132.
    Oom, Charlotte
    Linköpings universitet, Institutionen för medicinsk teknik.
    The influence of Ca2+ and Nitroprusside on the opening kinematics of the mitral valve2006Självständigt arbete på grundnivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats
    Abstract [en]

    During a cardiac cycle the cardiac walls change between contracted and relaxed and the valves open and close in response to pressure changes. This master thesis is a study of the changes in heart movement pattern caused by intravenous injections of Ca2+ or Nitroprusside. At Stanford University radiopaque markers have been surgically implanted in the walls and in the mitral valve of ovine hearts and 3D coordinates for each marker have been constantly measured during the cardiac cycle. By using MatLab, the volume and pressure of the left ventricle and several parameters related to the opening kinematics of the mitral valve have been analyzed. The results show, among others, that both Ca2+ and Nitroprusside reduce the volume and pressure of the left ventricle and that both substances decrease the size of the mitral annular ring. It was also shown that Ca2+ delays the opening of the mitral valve.

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  • 133.
    Oosterhuis, Wytze P.
    et al.
    Zuyderland Medical Centre, Netherlands.
    Bayat, Hassan
    Sina Medical Lab, Iran.
    Armbruster, David
    Abbott Labs, IL 60064 USA.
    Coskun, Abdurrahman
    Acibadem University, Turkey.
    Freeman, Kathleen P.
    IDEXX Labs Ltd, England.
    Kallner, Anders
    Karolinska University Hospital Stockholm, Sweden.
    Koch, David
    Emory University, GA 30322 USA.
    Mackenzie, Finlay
    University Hospital Birmingham NHS Fdn Trust, England.
    Migliarino, Gabriel
    Gmigliarino Consultants, Argentina.
    Orth, Matthias
    Vinzenz von Paul Kliniken gGmbH, Germany.
    Sandberg, Sverre
    University of Bergen, Norway; Haukeland Hospital, Norway.
    Sylte, Marit S.
    Haukeland Hospital, Norway; University of Bergen, Norway.
    Westgard, Sten
    Westgard QC, WI USA.
    Theodorsson, Elvar
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för mikrobiologi och molekylär medicin. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Diagnostikcentrum, Klinisk kemi.
    The use of error and uncertainty methods in the medical laboratory2018Ingår i: Clinical Chemistry and Laboratory Medicine, ISSN 1434-6621, E-ISSN 1437-4331, Vol. 56, nr 2, s. 209-219Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Error methods - compared with uncertainty methods - offer simpler, more intuitive and practical procedures for calculating measurement uncertainty and conducting quality assurance in laboratory medicine. However, uncertainty methods are preferred in other fields of science as reflected by the guide to the expression of uncertainty in measurement. When laboratory results are used for supporting medical diagnoses, the total uncertainty consists only partially of analytical variation. Biological variation, pre- and postanalytical variation all need to be included. Furthermore, all components of the measuring procedure need to be taken into account. Performance specifications for diagnostic tests should include the diagnostic uncertainty of the entire testing process. Uncertainty methods may be particularly useful for this purpose but have yet to show their strength in laboratory medicine. The purpose of this paper is to elucidate the pros and cons of error and uncertainty methods as groundwork for future consensus on their use in practical performance specifications. Error and uncertainty methods are complementary when evaluating measurement data.

  • 134.
    Parlak, Onur
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biosensorer och bioelektronik. Linköpings universitet, Tekniska högskolan.
    Tiwari, Atul
    Hawaii Corrosion Laboratory, Department of Mechanical Engineering, University of Hawaii at Manoa, 96822 Hawaii, USA.
    Turner, Anthony P. F.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biosensorer och bioelektronik. Linköpings universitet, Tekniska högskolan.
    Tiwari, Ashutosh
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biosensorer och bioelektronik. Linköpings universitet, Tekniska högskolan.
    Template-Directed Hierarchical Self-Assembly of Graphene Based Hybrid Structure for Electrochemical Biosensing2013Ingår i: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 49, s. 53-62Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A template-directed self-assembly approach, using functionalised graphene as a fundamental building block to obtain a hierarchically ordered graphene-enzyme-nanoparticle bioelectrode for electrochemical biosensing, is reported. An anionic surfactant was used to prepare a responsive, functional interface and direct the assembly on the surface of the graphene template. The surfactant molecules altered the electrostatic charges of graphene, thereby providing a convenient template-directed assembly approach to a free-standing planar sheet of sp(2) carbons. Cholesterol oxidase and cholesterol esterase were assembled on the surface of graphene by intermolecular attractive forces while gold nanoparticles are incorporated into the hetero-assembly to enhance the electro-bio-catalytic activity. Hydrogen peroxide and cholesterol were used as two representative analytes to demonstrate the electrochemical sensing performance of the graphene-based hybrid structure. The bioelectrode exhibited a linear response to H2O2 from 0.01 to 14 mM, with a detection limit of 25 nM (S/N=3). The amperometric response with cholesterol had a linear range from 0.05 to 0.35 mM, sensitivity of 3.14 mu A/mu M/cm(2) and a detection limit of 0.05 mu M. The apparent Michaelis-Menten constant (K-m(app)) was calculated to be 1.22 mM. This promising approach provides a novel methodology for template-directed bio-self-assembly over planar sp(2) carbons of a graphene sheet and furnishes the basis for fabrication of ultra-sensitive and efficient electrochemical biosensors.

  • 135.
    Pehrson Skidén, Ottar
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Automatic Exposure Correction And Local Contrast Setting For Diagnostic Viewing of Medical X-ray Images2010Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    To properly display digital X-ray images for visual diagnosis, a proper display range needs to be identified. This can be difficult when the image contains collimators or large background areas which can dominate the histograms. Also, when there are both underexposed and overexposed areas in the image it is difficult to display these properly at the same time. The purpose of this thesis is to find a way to solve these problems. A few different approaches are evaluated to find their strengths and weaknesses. Based on Local Histogram Equalization, a new method is developed to put various constraints on the mapping. These include alternative ways to perform the histogram calculations and how to define the local histograms. The new method also includes collimator detection and background suppression to keep irrelevant parts of the image out of the calculations. Results show that the new method enables proper display of both underexposed and overexposed areas in the image simultaneously while maintaining the natural look of the image. More testing is required to find appropriate parameters for various image types.

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  • 136.
    Petersson, Marcus
    Linköpings universitet, Institutionen för medicinsk teknik.
    Computational Modeling of Deep Brain Stimulation2007Självständigt arbete på grundnivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats
    Abstract [en]

    Deep brain stimulation (DBS) is a surgical treatment technique, which involves application of electrical pulses via electrodes inserted into the brain. Neurons, typically located in the basal ganglia network, are stimulated by the electrical field. DBS is currently widely used for symptomatically treating Parkinson’s disease patients and could potentially be used for a number of neurological diseases. In this study, computational modeling was used to simulate the electrical activity of neurons being affected by the electrical field, to gain better understanding of the mechanisms of DBS. The spatial and temporal distribution of the electrical field was coupled to a cable model representing a human myelinated axon. A passing fiber with ends infinitely far away was simulated. Results show that excitation threshold is highly dependent on the diameter of the fiber and the influence (threshold-distance and threshold-diameter relations) can be controlled to some extent, using charge-balanced biphasic pulses.

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    FULLTEXT01
  • 137.
    Pham, Tuan D.
    et al.
    Bioinformatics Research Group, School of Engineering and Information Technology, University of New South Wales, Canberra, ACT 2600, Australia.
    Salvetti, Federica
    Pisa University, Via Caruso, 14-56122 Pisa, Italy.
    Wang, Bing
    University of New South Wales, Canberra, ACT 2600, Australia.
    Diani, Marco
    Pisa University, Via Caruso, 14-56122 Pisa, Italy.
    Heindel, Walter
    University of M¨unster, A Schweitzer Straße 33, D-48129 M¨unster, University of M¨unster, A Schweitzer Straße 33, D-48129 M¨unster,Germany.
    Knecht, Stefan
    University of M¨unster, A Schweitzer Straße 33, D-48129 M¨unster, Germany.
    Wersching, Heike
    University of Munster, A Schweitzer Straße 33, D-48129 M¨unster, Germany/University of Munster, Domagkstraße.
    Baune, Bernhard T
    School of Medicine, University of Adelaide, SA 5005, Australia.
    Berger, Klaus
    University of M¨unster, Domagkstraße 3,Munster, Germany.
    The hidden-Markov brain comparison and inference of white matter hyperintensities on magnetic resonance imaging (MRI)2011Ingår i: Journal of Neural Engineering, ISSN 1741-2560, E-ISSN 1741-2552, Vol. 8, nr 1, s. 1-10Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rating and quantification of cerebral white matter hyperintensities on magnetic resonance imaging (MRI) are important tasks in various clinical and scientific settings. As manual evaluation is time consuming and imprecise, much effort has been made to automate the quantification of white matter hyperintensities. There is rarely any report that attempts to study the similarity/dissimilarity of white matter hyperintensity patterns that have different sizes, shapes and spatial localizations on the MRI. This paper proposes an original computational neuroscience framework for such a conceptual study with a standpoint that the prior knowledge about white matter hyperintensities can be accumulated and utilized to enable a reliable inference of the rating of a new white matter hyperintensity observation. This computational approach for rating inference of white matter hyperintensities, which appears to be the first study, can be utilized as a computerized rating-assisting tool and can be very economical for diagnostic evaluation of brain tissue lesions.

  • 138. Pirnejad, H.
    et al.
    Bal, R.
    Shahsavar, Nosrat
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    The nature of unintended effects of health information systems concerning patient safety: A systematic review with thematic synthesis.2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to understand the nature and causes through which Health Information Systems (HIS) can affect patient safety negatively, a systematic review with thematic synthesis of the qualitative studies was performed. 26 papers met our criteria and were included into content analysis. 40 error contributing factors in working with HIS were recognized. Upon which, 4 main categories of contributing factors were defined. Analysis of the semantic relation between contributing reasons and common types of errors in healthcare practice revealed 6 mechanisms that can function as secondary contributing reasons. Results of this study can support care providers, system designers, and system implementers to avoid unintended negative effects for patient safety.

  • 139.
    Rehn, Emelie
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Medicinska fakulteten.
    Modeling of scatter radiation during interventional X-ray procedures2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    During catheterized x-ray interventions the patient and medical staff is exposed to scatter radiation, as a consequence of tissue interactions. Ionizing radiation for medical purpose is potentially dangerous and can cause malignancy, skin damage and more. Studies have suggested an increase in the prevalence of eye lens cataract, thyroid cancer and left sided brain tumors in doctors. Therefore, it is mandatory to reduce the radiation dose in medicine, a principle known as ALARA (as low as Reasonably Achievable). Lead aprons, collars and shieldings are safety precautions to protect the team in the operating room. The x-ray equipment and surgical techniques are constantly evolving and the interventions become more complex which may increase the x-ray dose. Although x-ray imaging is required in interventional procedures endeavors of reducing radiation exposure to staff is of high interest. There is a need to increase the awareness about scatter radiation and radiation protection efforts are gaining momentum. Initiative to train a dose reducing behavior by education and awareness are key documents within the European Union’s guidelines on Radiation protection.

    The aims of this thesis were to create a 3D model for representation of real-time exposure and accumulated scatter radiation to staff performing interventional x-ray procedures and identify parameters that affect the scatter radiation.

    Extensive measurements were made with real time dosimeters while irradiating an anthropomorphic phantom. For five lateral C-arm projections, 68 - 80 data points each were used to measure scatter dose distribution around the patient. In the typical operator position, the effect of craniocaudal projection angle, patient size, field size, image detector height and pulse rate on scatter radiation dose was also investigated.

    It was possible to create a 3D model from interpolated measurement data that can generate dose rate with promising results. Six out of eight modelled doses deviated +/- 26.6 % from the validation cases. A model that delivers relative dose is an intuitive approach in education for interventional x-ray radiation safety. The staff position in relation to the x-ray source and the patient size have a significant correlation to the dose rate. Additional measurements are needed to ensure the reliability of the model. This work completes the effect of scatter radiation distribution around the patient table, which is not yet evaluated as thoroughly by other authors.

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  • 140.
    Rejmstad, Peter
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Zsigmond, Peter
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för neuro- och inflammationsvetenskap. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Sinnescentrum, Neurokirurgiska kliniken US.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Oxygen saturation estimation in brain tissue using diffuse reflectance spectroscopy along stereotactic trajectories2017Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 25, nr 7, s. 8192-8201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Diffuse reflectance spectroscopy (DRS) can be used to estimate oxygen saturation (SO2) of hemoglobin and blood fraction (fB) in brain tissue. The aim of the study was to investigate the SO2 and fB in different positions along deep brain stimulation (DBS) trajectories and in specific target regions using DRS and a novel algorithm. DRS measurements were done at 166 well-defined anatomical positions in relation to stereotactic DBS-implantation along 20 trajectories toward 4 DBS targets (STN, Vim, GPi and Zi). The measurements were dived into groups (gray, white and light gray matter) related to anatomical position, and DBS targets, before comparison and statistical analysis. The median SO2 in gray, white and light gray matter were 52%, 24% and 20%, respectively. Median fB in gray matter (3.9%) was different from values in white (1.0%, p < 0.05) and light gray (0.9%, p < 0.001) matter. No significant difference in median SO2 and fB was found between DBS target regions. The novel algorithm allows for quick and reliable estimation of SO2 and fB in human brain tissue.

  • 141.
    Rejmstad, Peter
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Åkesson, Gustav
    Östergötlands Läns Landsting, Sinnescentrum, Neurokirurgiska kliniken US.
    Åneman, Oscar
    Östergötlands Läns Landsting, Sinnescentrum, Neurokirurgiska kliniken US. Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för neuro- och inflammationsvetenskap. Linköpings universitet, Medicinska fakulteten.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    A laser Doppler system for monitoring of cerebral microcirculation: implementation and evaluation during neurosurgery2016Ingår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, ISSN 0140-0118, Vol. 54, nr 1, s. 123-131Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this study was to adapt and evaluate laser Doppler perfusion monitoring (LDPM) together with custom designed brain probes and software for continuous recording of cerebral microcirculation in patients undergoing neurosurgery. The LDPM system was used to record perfusion and backscattered light (TLI). These parameters were displayed together with the extracted heart rate (HR), pulsatility index (PI) and signal trends from adjustable time intervals. Technical evaluation was done on skin during thermal provocation. Clinical measurements were performed on ten patients undergoing brain tumour surgery. Data from 76 tissue sites were captured with a length varying between 10 s to 15 min. Statistical comparisons were done using Mann-Whitney tests. Grey and tumour tissue could be separated from white matter using the TLI-signal (p < 0.05). The perfusion was significantly higher in grey and tumour tissue compared to white matter (p < 0.005). LDPM was successfully used as an intraoperative tool for monitoring local blood flow and additional parameters linked to cerebral microcirculation (perfusion, TLI, heart rate and PI) during tumour resection. The systems stability opens up for studies in the postoperative care of patients with e.g. traumatic brain injury or subarachnoid haemorrhage.

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  • 142. Beställ onlineKöp publikationen >>
    Richter, Johan
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Fluorescence Guided Resection of Brain Tumors: Evaluation of a Hand-held Spectroscopic Probe2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Maligna hjärntumörer växer infiltrerande i hjärnan och kan därförinte helt avlägsnas genom kirurgiska operationer. För en optimerad behandling har det emellertid visat sig vara av värde att avlägsna såmycket som möjligt av tumörvävnaden. Identifiering av tumören i gränszonen är mycket svårt, men avgörande. Studier har visat att visualisering av den specifika laddningen av 5-aminolevulinsyra (5-ALA) i tumören kan bidra till att maximera resektionen. Institutionen för Medicinsk Teknik (IMT) på Linköpings universitet,har utvecklat en liten handhållen optisk prob (HHP) för att identifiera tumörvävnad med hög känslighet med hjälp avfluorescens-spektroskopi.

    Den tekniska konstruktionen och de optiska egenskaperna hos proben utvecklades stegvis genom testning i flera neurokirurgiska operationer för resektion av maligna gliom. Utrustningen uppfyllde alla krav när det gällde steril hantering i operationssalen och kunde användas utan störningar av något slag med annan operationsutrustning. Integreringen i ett navigerings-system och användningen i kombination med ett kirurgiskt mikroskop för fluorescens-styrd kirurgi var oproblematiska. Mätningar under 27 operationer vid resektion av maligna gliom jämfördes med resultat från biopsier från samma tumörtagningsställen. Utrustningen testades såväl som en fristående enhet (n = 180) och som integrerad i ett navigationssystem eller i kombination med mikroskopet (n =190). En särskild kvot beräknad ur mätningarna möjliggjorde objektiva och jämförbara värden för olika vävnader, i överensstämmelse med resultaten från de vävnadspatologiska undersökningarna och i överensstämmelse med navigationssystemet såväl som med det kirurgiska mikroskopet.

    Tumörernas gränszon undersöktes och tumörfluorescens kunde identifieras bortom fluorescensen som mikroskopet visade. En högre känslighet hos HHP bekräftades; specificiteten var lägre. Den kombinerade användningen av HHP med ett navigationssystem och med ett kirurgiskt mikroskop visade sig vara fördelaktig.

    Delarbeten
    1. Evaluation of a Fiber-Optic Fluorescence Spectroscopy System to Assist Neurosurgical Tumor Resections
    Öppna denna publikation i ny flik eller fönster >>Evaluation of a Fiber-Optic Fluorescence Spectroscopy System to Assist Neurosurgical Tumor Resections
    Visa övriga...
    2007 (Engelska)Ingår i: Novel Optical Instrumentation for Biomedical Applications III (Proceedings Volume) / [ed] Christian D. Depeursinge, Bellingham, Washington, USA: SPIE - International Society for Optical Engineering, 2007, Vol. 6631, s. 66310W-1-66310W-8Konferensbidrag, Publicerat paper (Övrigt vetenskapligt)
    Abstract [en]

    The highly malignant brain tumor, glioblastoma multiforme, is difficult to totally resect without aid due to its infiltrative way of growing and its morphological similarities to surrounding functioning brain under direct vision in the operating field. The need for an inexpensive and robust real-time visualizing system for resection guiding in neurosurgery has been formulated by research groups all over the world. The main goal is to develop a system that helps the neurosurgeon to make decisions during the surgical procedure. A compact fiber optic system using fluorescence spectroscopy has been developed for guiding neurosurgical resections. The system is based on a high power light emitting diode at 395 nm and a spectrometer. A fiber bundle arrangement is used to guide the excitation light and fluorescence light between the instrument and the tissue target. The system is controlled through a computer interface and software package especially developed for the application. This robust and simple instrument has been evaluated in vivo both on healthy skin but also during a neurosurgical resection procedure. Before surgery the patient received orally a low dose of 5-aminolevulinic acid, converted to the fluorescence tumor marker protoporphyrin IX in the malignant cells. Preliminary results indicate that PpIX fluorescence and brain tissue autofluorescence can be recorded with the help of the developed system intraoperatively during resection of glioblastoma multiforme.

    Ort, förlag, år, upplaga, sidor
    Bellingham, Washington, USA: SPIE - International Society for Optical Engineering, 2007
    Serie
    Proceedings of SPIE - International Society for Optical Engineering, ISSN 0277-786X ; Vol. 6631
    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-38407 (URN)10.1117/12.728546 (DOI)44225 (Lokalt ID)9780819467751 (ISBN)44225 (Arkivnummer)44225 (OAI)
    Konferens
    Novel optical instrumentation for biomedical applications III : 17-19 June 2007, Munich, Germany
    Tillgänglig från: 2009-10-10 Skapad: 2009-10-10 Senast uppdaterad: 2018-03-23Bibliografiskt granskad
    2. Optical Touch Pointer for Fluorescence Guided Glioblastoma Resection Using 5-Aminolevulinic Acid
    Öppna denna publikation i ny flik eller fönster >>Optical Touch Pointer for Fluorescence Guided Glioblastoma Resection Using 5-Aminolevulinic Acid
    2010 (Engelska)Ingår i: Lasers in Surgery and Medicine, ISSN 0196-8092, E-ISSN 1096-9101, Vol. 42, nr 1, s. 9-14Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Background and Objective

    Total tumor resection in patients with glioblastoma multiforme (GBM) is difficult to achieve due to the tumor's infiltrative way of growing and morphological similarity to the surrounding functioning brain tissue. The diagnosis is usually subjectively performed using a surgical microscope. The objective of this study was to develop and evaluate a hand-held optical touch pointer using a fluorescence spectroscopy system to quantitatively distinguish healthy from malignant brain tissue intraoperatively.

    Study Design/Materials and Methods

    A fluorescence spectroscopy system with pulsed modulation was designed considering optimum energy delivery to the tissue, minimal photobleaching of PpIX and omission of the ambient light background in the operating room (OR). 5-Aminolevulinic acid (5-ALA) of 5 mg/kg body weight was given to the patients with a presumed GBM prior to surgery. During the surgery a laser pulse at 405 nm was delivered to the tissue. PpIX in glioblastoma tumor cells assigned with peaks at 635 and 704 nm was detected using a fiber optical probe.

    Results/Conclusion

    By using the pulsed fluorescence spectroscopy, PpIX fluorescence is quantitatively detected in the GBM. An effective suppression of low power lamp background from the recorded spectra in addition to a significant reduction of high power surgical lights is achieved.

    Ort, förlag, år, upplaga, sidor
    Wiley-Blackwell, 2010
    Nyckelord
    background light suppression • fluorescence spectroscopy • glioblastoma multiforme • intraoperative
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-53946 (URN)10.1002/lsm.20868 (DOI)
    Tillgänglig från: 2010-02-15 Skapad: 2010-02-15 Senast uppdaterad: 2017-12-12Bibliografiskt granskad
    3. Fluorescence Spectroscopy Measurements in Ultrasonic Navigated Resection of Malignant Brain Tumors
    Öppna denna publikation i ny flik eller fönster >>Fluorescence Spectroscopy Measurements in Ultrasonic Navigated Resection of Malignant Brain Tumors
    2011 (Engelska)Ingår i: Lasers in Surgery and Medicine, ISSN 0196-8092, E-ISSN 1096-9101, Vol. 43, nr 1, s. 8-14Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Background and Objective: Glioblastoma multiforme is a highly malignant primary brain tumor. It has no border but at best a marginal zone, however, invisible to the surgeon. An optical touch pointer (OTP) enabling differentiation of healthy and tumor tissue by means of fiber-optic fluorescence spectroscopy has been developed. In combination with an ultrasonic navigation system, the OTP may be used for demarcation of resectable tumor tissue. The aim of the study was to evaluate the clinical performance of OTP during surgery of malignant brain tumors. 

    Study Design/Materials and Methods: Nine patients were operated on with the standard surgical procedure, including white light microscopy and navigation. A total of 5 mg/kg bodyweight of 5-amino-levulin acid was orally administrated before surgery. The OTP was calibrated into the ultrasound-based navigation system and measurements were performed in tumor core and along the tumor border. The ratio between the protoporphyrin IX fluorescence at 635 nm and the autofluorescence was used for quantifications of data. Biopsies (n =20), ultrasound images (n = 30), and visual inspection (n =180) were compared to the fluorescence ratio. 

    Results/Conclusion : Healthy and tumor tissue could be identified and differentiated with the OTP(P < 0.001). The fluorescence ratio in average was 0 outside the tumor and low in the gliotic edema zone around the tumor. It increased in the marginal zone and was highest in the solid tumor tissue. In the necrotic tissue, in the center of the tumor, the ratio in average was 0. The OTP can be used in combination with ultrasound-based navigation and may help to determine whether to resect otherwise not identifiable tissue.

    Nyckelord
    5-amino-levulin acid (5-ALA);fluorescence-guided resection (FGR);glioblastoma multiforme;optical touch pointer (OTP);protoporphyrin IX (PpIX) fluorescence;ultrasound navigation
    Nationell ämneskategori
    Medicinsk laboratorie- och mätteknik
    Identifikatorer
    urn:nbn:se:liu:diva-64689 (URN)10.1002/lsm.21022 (DOI)000286440300002 ()
    Tillgänglig från: 2011-02-01 Skapad: 2011-02-01 Senast uppdaterad: 2017-12-11Bibliografiskt granskad
    4. Combination of Hand-Held Probe and Microscopy for Fluorescence Guided Surgery in the Brain Tumor Marginal Zone
    Öppna denna publikation i ny flik eller fönster >>Combination of Hand-Held Probe and Microscopy for Fluorescence Guided Surgery in the Brain Tumor Marginal Zone
    2017 (Engelska)Ingår i: Photodiagnosis and Photodynamic Therapy, ISSN 1572-1000, Vol. 18, s. 185-192Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Background

    Visualization of the tumor is crucial for differentiating malignant tissue from healthy brain during surgery, especially in the tumor marginal zone. The aim of the study was to introduce a fluorescence spectroscopy-based hand-held probe (HHF-probe) for tumor identification in combination with the fluorescence guided resection surgical microscope (FGR-microscope), and evaluate them in terms of diagnostic performance and practical aspects of fluorescence detection.

    Material and Methods

    Eighteen operations were performed on 16 patients with suspected high-grade glioma. The HHF-probe and the FGR-microscope were used for detection of protoporphyrin (PpIX) fluorescence induced by 5-aminolevulinic acid (5-ALA) and evaluated against histopathological analysis and visual grading done through the FGR-microscope by the surgeon. A ratio of PpIX fluorescence intensity to the autofluorescence intensity (fluorescence ratio) was used to quantify the spectra detected by the probe.

    Results

    Fluorescence ratio medians (range 0 – 40) measured by the probe were related to the intensity of the fluorescence in the FGR-microscope, categorized as “none” (0.3, n = 131), “weak” (1.6, n = 34) and “strong” (5.4, n = 28). Of 131 “none” points in the FGR-microscope, 88 (67%) exhibited fluorescence with the HHF-probe. For the tumor marginal zone, the area under the receiver operator characteristics (ROC) curve was 0.49 for the FGR-microscope and 0.65 for the HHF-probe.

    Conclusions

    The probe was integrated in the established routine of tumor resection using the FGR-microscope. The HHF-probe was superior to the FGR-microscope in sensitivity; it detected tumor remnants after debulking under the FGR-microscope. The combination of the HHF-probe and the FGR-microscope was beneficial especially in the tumor marginal zone.

    Ort, förlag, år, upplaga, sidor
    Amsterdam: Elsevier, 2017
    Nyckelord
    High-grade glioma, Fluorescence guided resection (FGR), 5-Aminolaevulinic acid (5-ALA), Fluorescence spectroscopy, Protoporphyrin (PpIX)
    Nationell ämneskategori
    Medicinteknik
    Identifikatorer
    urn:nbn:se:liu:diva-134849 (URN)10.1016/j.pdpdt.2017.01.188 (DOI)000404315000028 ()28223144 (PubMedID)
    Anmärkning

    Funding agencies: Swedish Governmental Agency for Innovation Systems (Vinnova); Swedish Foundation for Strategic Research (SSF); Swedish Research Council (VR) [311-2006-7661, 523-2013-2735]; NovaMedTech; Swedish Childhood Cancer Foundation [MT 2013-0043]; ALF Grants Region

    Tillgänglig från: 2017-03-08 Skapad: 2017-03-08 Senast uppdaterad: 2019-10-14Bibliografiskt granskad
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  • 143.
    Richter, Johan C.O.
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan. Östergötlands Läns Landsting, Rekonstruktionscentrum, Neurokirurgiska kliniken US.
    Haj-Hosseini, Neda
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Andersson-Engels, Stefan
    Department of Physics, Lund University.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Fluorescence Spectroscopy Measurements in Ultrasonic Navigated Resection of Malignant Brain Tumors2011Ingår i: Lasers in Surgery and Medicine, ISSN 0196-8092, E-ISSN 1096-9101, Vol. 43, nr 1, s. 8-14Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background and Objective: Glioblastoma multiforme is a highly malignant primary brain tumor. It has no border but at best a marginal zone, however, invisible to the surgeon. An optical touch pointer (OTP) enabling differentiation of healthy and tumor tissue by means of fiber-optic fluorescence spectroscopy has been developed. In combination with an ultrasonic navigation system, the OTP may be used for demarcation of resectable tumor tissue. The aim of the study was to evaluate the clinical performance of OTP during surgery of malignant brain tumors. 

    Study Design/Materials and Methods: Nine patients were operated on with the standard surgical procedure, including white light microscopy and navigation. A total of 5 mg/kg bodyweight of 5-amino-levulin acid was orally administrated before surgery. The OTP was calibrated into the ultrasound-based navigation system and measurements were performed in tumor core and along the tumor border. The ratio between the protoporphyrin IX fluorescence at 635 nm and the autofluorescence was used for quantifications of data. Biopsies (n =20), ultrasound images (n = 30), and visual inspection (n =180) were compared to the fluorescence ratio. 

    Results/Conclusion : Healthy and tumor tissue could be identified and differentiated with the OTP(P < 0.001). The fluorescence ratio in average was 0 outside the tumor and low in the gliotic edema zone around the tumor. It increased in the marginal zone and was highest in the solid tumor tissue. In the necrotic tissue, in the center of the tumor, the ratio in average was 0. The OTP can be used in combination with ultrasound-based navigation and may help to determine whether to resect otherwise not identifiable tissue.

  • 144. Beställ onlineKöp publikationen >>
    Roback, Kerstin
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk teknologiutvärdering. Linköpings universitet, Tekniska högskolan.
    Medical Device Innovation: The integrated processes of invention, diffusion and deployment2006Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    An increased use of medical devices has been assumed to be a major cause of rising healthcare expenditures. Nations around the world are trying to keep costs down, but strong incentives still exist for the development and use of new devices. Innovation is, however, never exclusively good or bad and it is not easy to evaluate the net effect. Theories and empirical research on innovation have been produced for more than 100 years. In this, the diffusion of innovations has attracted the most interest, while other areas, such as the integration of technologies, have been less thoroughly researched.

    This thesis presents a model of medical device innovation in hospitals – from the first idea and invention effort to regular use of a new technology. The suggested model is built on three fundaments: (1) academic innovation literature, (2) empirical studies, and (3) observations of on-going innovation processes. The model is a synthesis of the accumulated knowledge in different innovation research traditions, and of empirical studies of the Swedish healthcare system and the medical device industry. The aim is to give a comprehensive picture of the innovation process, and to provide a theoretical model, which can be used for studying and influencing the paths of medical device innovations into healthcare practice.

    In order to achieve a balanced rate of change, with long-term societal benefits, an inter-disciplinary approach is necessary in the planning and regulation of medical device innovation. The new model combines academic views with political/entrepreneurial and healthcare views. Innovation, in this model, is suggested to occur in three integrated activity domains: invention, diffusion, and deployment. A great number of factors that influence these activities are investigated and described, and different roles and incentives are discussed. Deviations from traditional innovation theory are for example: (a) integration of invention activities as having an impact on later events; (b) inclusion of the inventor/developer as a main actor also in the diffusion and deployment domains; (c) increased focus of the concept of technology cluster innovation, and (d) the rationality of use and abandonment of knowledge as factors to be included in the estimation of consequences of innovation.

    Finally, the thesis suggests a number of model and methodology improvements and policy implications for management of innovation in hospitals.

    Delarbeten
    1. Transfer of health care technology in university-industry research collaboration environment
    Öppna denna publikation i ny flik eller fönster >>Transfer of health care technology in university-industry research collaboration environment
    2001 (Engelska)Ingår i: Engineering in Medicine and Biology Society. Proceedings of the 23rd Annual International Conference of the IEEE, 2001, Vol. 4, s. 3938-3941Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    The traditional innovation research has focused on the diffusion process and adoption of new technologies. This paper deals with health care technology in the early innovation stages preceding targeted development and marketing. A model of early research processes in the biomedical field and determinants of technology transfer will be presented. The study material is eleven projects in the Competence Center Noninvasive Medical Measurements (NIMED), Linkoping University, which is a collaboration center where academic researchers cooperate with industry and clinical departments. Data collection was made through semi-structured interviews. A qualitative approach has been adopted for data analysis. Research initiatives of the investigated projects do in most cases originate in the academic knowledge base and earlier connections in industry and health care play an important role in the formation of cooperation constellation. A number of internal factors are perceived as positive to project advancement, such as stable economy, proximity to clinical departments, and positive feedback from collaboration partners. Significant negative factors are all related to changes in cooperation structure. Clusters of related projects seem to be beneficial to research work and is an evident external factor which has to be added in a new model of technology transfer.

    Nationell ämneskategori
    Medicinsk laboratorie- och mätteknik
    Identifikatorer
    urn:nbn:se:liu:diva-14140 (URN)
    Tillgänglig från: 2006-11-13 Skapad: 2006-11-13
    2. A New Fiberoptical Respiratory Rate Monitor for the Neonatal Intensive Care Unit
    Öppna denna publikation i ny flik eller fönster >>A New Fiberoptical Respiratory Rate Monitor for the Neonatal Intensive Care Unit
    Visa övriga...
    2005 (Engelska)Ingår i: Pediatric Pulmonology, ISSN 8755-6863, Vol. 39, nr 2, s. 120-126Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    A new technique for respiratory rate measurement in the neonatal intensive care unit, fiberoptic respirometry (FORE), was tested using a specially designed nasal adapter. The aim was to investigate the system's accuracy and compare it to the transthoracic impedance (TTI) method and manual counting (MC). Further, the relationship between accuracy and degree of body movement was investigated. Seventeen neonates of median gestational age 35 weeks were included in the study. Video recordings (synchronized with data recordings) were used for classification of body movement. Breaths per minute data were obtained for 23-32-min periods per child, and a subset of these included MC performed by experienced nurses. A Bland-Altman analysis showed low accuracy of both FORE and TTI. A >20% deviation from MC was found in 22.7% and 23.8% of observations for the two methods, respectively. Both methods had accuracy problems during body movement. FORE tended to underestimate respiratory rate due to probe displacement, while TTI overestimated due to motion artefacts. The accuracy was also strongly subject-dependent. The neonates were undisturbed by the FORE device. In some cases, though, it was difficult to keep the adapter positioned in the airway. Further development should, therefore, focus on FORE adapter improvements to maintain probe position over time.

    Nyckelord
    respiratory rate, neonatal monitoring, prematurity, optical sensors, intensive care, apnea
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-14141 (URN)10.1002/ppul.20137 (DOI)
    Tillgänglig från: 2006-11-13 Skapad: 2006-11-13 Senast uppdaterad: 2009-05-29
    3. Home informatics in healthcare: Assessment guidelines to keep up quality of care and avoid adverse effects
    Öppna denna publikation i ny flik eller fönster >>Home informatics in healthcare: Assessment guidelines to keep up quality of care and avoid adverse effects
    2003 (Engelska)Ingår i: Technology and Health Care - European Society for Engineering and Medicine, ISSN 0928-7329, Vol. 11, nr 3, s. 195-206Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Due to an ageing population and improved treatment possibilities, a shortage in hospital beds is a fact in many countries. Home healthcare schemes using information technology (IT) are under development as a response to this and with the intention to produce a more cost-effective care. So far it has been shown that home healthcare is beneficial to certain patient groups. The trend is a widening of the criteria for admission to home healthcare, which means treatment in the home of more severe conditions that otherwise would require in-hospital care. Home informatics has the potential to become a means of providing good care at home. In this process, it is important to consider what new risks will be encountered when placing electronic equipment in the home care environment. Continuous assessment and guidance is important in order to achieve a safe and effective care. Based on a review of current knowledge this paper presents an inventory of risks and adverse events specific to this area. It was found that risks and adverse events could stem from technology in itself, from human-technology interaction conditions or from the environment in which the technology is placed. As a result from the risk inventory, this paper proposes guidelines for the planning and assessment of IT-based hospital-at-home schemes . These assessment guidelines are specifically aimed at performance improvement and thus to be considered a complement to the more general guidelines on telehomecare adopted by the American Telemedicine Association (ATA) in October 2002.

    Nyckelord
    assessment, home informatics, hospital-at-home, telehomecare
    Nationell ämneskategori
    Medicinsk laboratorie- och mätteknik
    Identifikatorer
    urn:nbn:se:liu:diva-14142 (URN)
    Tillgänglig från: 2006-11-13 Skapad: 2006-11-13
    4. Adoption of medical devices: Perspectives of professionals in Swedish neonatal intensive care
    Öppna denna publikation i ny flik eller fönster >>Adoption of medical devices: Perspectives of professionals in Swedish neonatal intensive care
    2007 (Engelska)Ingår i: Technology and Health Care, ISSN 0928-7329, Vol. 15, nr 3, s. 157-179Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Advances in biomedical engineering enable us to treat increasingly severe conditions. This implies an increased need for regulation and priority setting in healthcare, to ensure appropriate safety cautions and to avoid accelerating expenditures. This interview study investigates the mechanisms behind the adoption and use of medical devices through the subjective experiences of hospital staff working with devices for neonatal intensive care. The adoption was found to be primarily initiated by vendor activities, but professionals preferably sought information about functionality from close colleagues. Full integration of devices was sometimes not achieved, and even though the adopting units had good introduction routines, there was no systematic follow-up of how adopted devices had been integrated in the work practices. Diffusion variations were, however, mainly found for temporarily tested devices and not for permanently available technologies. Three factors were found to be the major explanatory variables of the adoption of medical devices: (1) the subjective expected value of the device, (2) information and learning, and (3) the innovativeness of the adopting unit.

    Nyckelord
    Diffusion, innovation, adoption, medical devices, neonatal intensive care, decision-making, healthcare management
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-14143 (URN)130.236.83.89 (DOI)
    Tillgänglig från: 2006-11-13 Skapad: 2006-11-13 Senast uppdaterad: 2009-05-12
    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 145.
    Roback, Kerstin
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk teknologiutvärdering. Linköpings universitet, Tekniska högskolan.
    Hass, Ursula
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk teknologiutvärdering. Linköpings universitet, Tekniska högskolan.
    Persson, Jan
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk teknologiutvärdering. Linköpings universitet, Tekniska högskolan.
    Transfer of health care technology in university-industry research collaboration environment2001Ingår i: Engineering in Medicine and Biology Society. Proceedings of the 23rd Annual International Conference of the IEEE, 2001, Vol. 4, s. 3938-3941Konferensbidrag (Refereegranskat)
    Abstract [en]

    The traditional innovation research has focused on the diffusion process and adoption of new technologies. This paper deals with health care technology in the early innovation stages preceding targeted development and marketing. A model of early research processes in the biomedical field and determinants of technology transfer will be presented. The study material is eleven projects in the Competence Center Noninvasive Medical Measurements (NIMED), Linkoping University, which is a collaboration center where academic researchers cooperate with industry and clinical departments. Data collection was made through semi-structured interviews. A qualitative approach has been adopted for data analysis. Research initiatives of the investigated projects do in most cases originate in the academic knowledge base and earlier connections in industry and health care play an important role in the formation of cooperation constellation. A number of internal factors are perceived as positive to project advancement, such as stable economy, proximity to clinical departments, and positive feedback from collaboration partners. Significant negative factors are all related to changes in cooperation structure. Clusters of related projects seem to be beneficial to research work and is an evident external factor which has to be added in a new model of technology transfer.

  • 146.
    Roback, Kerstin
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk teknologiutvärdering. Linköpings universitet, Tekniska högskolan.
    Herzog, Almut
    Linköpings universitet, Institutionen för datavetenskap, IISLAB - Laboratoriet för intelligenta informationssystem. Linköpings universitet, Tekniska högskolan.
    Home informatics in healthcare: Assessment guidelines to keep up quality of care and avoid adverse effects2003Ingår i: Technology and Health Care - European Society for Engineering and Medicine, ISSN 0928-7329, Vol. 11, nr 3, s. 195-206Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Due to an ageing population and improved treatment possibilities, a shortage in hospital beds is a fact in many countries. Home healthcare schemes using information technology (IT) are under development as a response to this and with the intention to produce a more cost-effective care. So far it has been shown that home healthcare is beneficial to certain patient groups. The trend is a widening of the criteria for admission to home healthcare, which means treatment in the home of more severe conditions that otherwise would require in-hospital care. Home informatics has the potential to become a means of providing good care at home. In this process, it is important to consider what new risks will be encountered when placing electronic equipment in the home care environment. Continuous assessment and guidance is important in order to achieve a safe and effective care. Based on a review of current knowledge this paper presents an inventory of risks and adverse events specific to this area. It was found that risks and adverse events could stem from technology in itself, from human-technology interaction conditions or from the environment in which the technology is placed. As a result from the risk inventory, this paper proposes guidelines for the planning and assessment of IT-based hospital-at-home schemes . These assessment guidelines are specifically aimed at performance improvement and thus to be considered a complement to the more general guidelines on telehomecare adopted by the American Telemedicine Association (ATA) in October 2002.

  • 147.
    Romu, Thobias
    et al.
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Borga, Magnus
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Tekniska högskolan.
    Dahlqvist Leinhard, Olof
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Hälsouniversitetet.
    MANA - Multi scale adaptive normalized averaging2011Ingår i: 2011 IEEE International Symposium on Biomedical Imaging: From Nano to Macro, IEEE conference proceedings, 2011, s. 361-364Konferensbidrag (Refereegranskat)
    Abstract [en]

    It is possible to correct intensity inhomogeneity in fat–water Magnetic Resonance Imaging (MRI) by estimating a bias field based on the observed intensities of voxels classified as the pure adipose tissue. The same procedure can also be used to quantify fat volume and its distribution which opens up for new medical applications. The bias field estimation method has to be robust since pure fat voxels are irregularly located and the density varies greatly within and between image volumes. This paper introduces Multi scale Adaptive Normalized Average (MANA) that solves this problem bybasing the estimate on a scale space of weighted averages. By usingthe local certainty of the data MANA preserves details where the local data certainty is high and provides realistic values in sparse areas.

  • 148.
    Romu, Thobias
    et al.
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Dahlqvist Leinhard, Olof
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Hälsouniversitetet.
    Forsgren, Mikael
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Almer, Sven
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Gastroenterologi och hepatologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Dahlström, Nils
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet.
    Kechagias, Stergios
    Linköpings universitet, Institutionen för medicin och hälsa, Internmedicin. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Nyström, Fredrik
    Linköpings universitet, Institutionen för medicin och hälsa, Internmedicin. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Smedby, Örjan
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Diagnostikcentrum, Röntgenkliniken i Linköping.
    Lundberg, Peter
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Borga, Magnus
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Tekniska högskolan.
    Fat Water Classification of Symmetrically Sampled Two-Point Dixon Images Using Biased Partial Volume Effects2011Ingår i: Proceedings of the annual meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2011), 2011., 2011Konferensbidrag (Refereegranskat)
  • 149.
    Rovai, Daniele
    et al.
    CNR, Institute of Clinical Physiology, Pisa, Italy.
    Janerot-Sjöberg, Birgitta
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Nagy, András
    Gottsegen György Hungarian Institute of Cardiology, Budapest, Hungary.
    Marini, Cecilia
    CNR, Institute of Clinical Physiology, Pisa, Italy.
    Burchielli, Silvia
    CNR, Institute of Clinical Physiology, Pisa, Italy.
    Castellari, Michele
    CNR, Institute of Clinical Physiology, Pisa, Italy.
    Morales, Maria-Aurora
    CNR, Institute of Clinical Physiology, Pisa, Italy.
    Trivella, M. Giovanna
    CNR, Institute of Clinical Physiology, Pisa, Italy.
    Ostensen, Jonny
    Nycomed Imaging AS, Oslo, Norway.
    Distante, Allessandro
    University of Pisa, Pisa, Italy.
    L'Abbate, Antonio
    CNR, Institute of Clinical Physiology, Pisa, Italy.
    Myocardial perfusion abnormalities by intravenous administration of the contrast agent NC100100 in an experimental model of coronary artery occlusion and reperfusion1998Ingår i: Echocardiography, ISSN 0742-2822, E-ISSN 1540-8175, Vol. 15, nr 8, s. 731-740Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this study was to evaluate a second-generation echo contrast agent (NC100100) for the study of myocardial perfusion. In eight anesthetized open-chest dogs, this agent was injected intravenously under baseline conditions, during acute coronary thrombosis, and after reperfusion, using both fundamental (FI) and harmonic (HI) imaging, both continuous and intermittent imaging, and both ultrasound (US) and integrated backscatter (IBS) imaging. Contrast injections did not modify the hemodynamic parameters. With all imaging modalities, myocardial contrast enhancement (MCE) was higher with intermittent than with continuous imaging (134 vs 82 gray level/pixel using FI, P = 0.02; 62 vs 32 acoustic units using US HI, P = 0.02; and 52 vs 12 dB using IBS, P = 0.05). MCE equally increased using either US or IBS imaging. The accuracy of MCE in detecting perfusion defects during coronary occlusion and myocardial reperfusion after thrombolysis was very good (sensitivity and specificity = 93% and 95% and 89% and 93%, respectively). The extent of myocardial perfusion defects by echo contrast showed a closer correlation with microspheres using HI (r = 0.82) than FI (r = 0.53). Thus, the intravenous administration of NC100100 during intermittent HI allows myocardial perfusion abnormalities to be accurately detected during acute myocardial infarction.

  • 150.
    Rowa, Per
    et al.
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Antonsson, Dan
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Automated Malaria Parasite Detection1977Rapport (Övrigt vetenskapligt)
    Abstract [en]

    A system for malaria parasite detection in thin blood-smears is presented. Sample slides prepared with standard methods are accepted. A low-cost TV-camera mounted on an ordinary microscope with a computer controlled stage is used as a picture sensor. Frames, digitized in windows of 64 x 64 pixels are fed into a special purpose picture processor at normal frame rate (25 frames/sec). In the picture processor measurements are made on the images at high speed. The classification problem is split into different levels each having different characteristics such as different sampling density. Four classes, three of which are different types of malaria parasites, are recognized. As a whole the classification is best labelled as a sequential pattern recognition procedure.

    In its preliminary version the system has been run at a speed comparable to that of a human operator, that is l 500 cells per minute. A test on 80 000 cells gave 25 false negatives out of 283 parasites (9%) and 41 false positives (0.05%).

    Ladda ner fulltext (pdf)
    Automated Malaria Parasite Detection
12345 101 - 150 av 207
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