liu.seSearch for publications in DiVA
Change search
Refine search result
123 1 - 50 of 135
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Agnvall, Beatrix
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Bélteky, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Jensen, Per
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Brain size is reduced by selectionfor tameness in Red Junglefowl–correlated effects in vital organs2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 3306Article in journal (Refereed)
    Abstract [en]

    During domestication animals have undergone changes in size of brain and other vital organs. We hypothesize that this could be a correlated effect to increased tameness. Red Junglefowl (ancestors of domestic chickens) were selected for divergent levels of fear of humans for five generations. The parental (P0) and the fifth selected generation (S5) were culled when 48–54 weeks old and the brains were weighed before being divided into telencephalon, cerebellum, mid brain and optic lobes. Each single brain part as well as the liver, spleen, heart and testicles were also weighed. Brains of S5 birds with high fear scores (S5 high) were heavier both in absolute terms and when corrected for body weight. The relative weight of telencephalon (% of brain weight) was significantly higher in S5 high and relative weight of cerebellum was lower. Heart, liver, testes and spleen were all relatively heavier (% of body weight) in S5 high. Hence, selection for tameness has changed the size of the brain and other vital organs in this population and may have driven the domesticated phenotype as a correlated response.

  • 2.
    Al-Absi, Thabit
    Linköping University, Department of Physics, Chemistry and Biology, Bioinformatics. Linköping University, The Institute of Technology.
    Efficient Characterization of Short Anelloviruses Fragments Found in Metagenomic Samples2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Some viral metagenomic serum samples contain a huge amount of Anellovirus, which is a genetically diverse family with a few conserved regions making it hard to efficiently characterize. Multiple sequence alignment of the Anelloviruses found in the sample must be constructed to get a clear picture of Anellovirus diversity and to identify stable regions. Using available multiple sequence alignment software directly on these fragments results in an MSA of a very poor quality due to their diversity, misaligned regions and low-quality regions present in the sequence.

    An efficient MSA must be constructed in order to characterize these Anellovirus present in the samples. Pairwise alignment is used to align one fragment to the database sequences at a time. The fragments are then aligned to the database sequences using the start and end position from the pairwise alignment results. The algorithm will also exclude non-aligned portions of the fragments, as these are very hard to handle properly and are often products of misassembly or chimeric sequenced fragments. Other tools to aid further analysis were developed, such as finding a non-overlapping window that contains the most fragments, find consensus of the alignment and extract any regions from the MSA for further analysis.

    An MSA was constructed with a high percent of correctly aligned bases compared to an MSA constructed using MSA softwares. The minimal number of genomes found in the sampled sequence was found as well as a distribution of the fragments along the database sequence. Moreover, highly conserved region and the window containing most fragments were extracted from the MSA and phylogenetic trees were constructed for these regions. 

  • 3.
    Alonso, Fabiola
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Modeling and simulation of DBS – comparison between leads and stimulation modes2014Conference paper (Other academic)
  • 4.
    Alonso, Fabiola
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Models and Simulations of the Electric Field in Deep Brain Stimulation: Comparison of Lead Designs, Operating Modes and Tissue Conductivity2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Deep brain stimulation (DBS) is an established surgical therapy for movement disorders such as Parkinson’s disease (PD) and essential tremor (ET). A thin electrode is implanted in a predefined area of the brain with the use of stereotactic neurosurgery. In the last few years new DBS electrodes and systems have been developed with possibilities for using more parameters for control of the stimulation volume.

    In this thesis, simulations using the finite element method (FEM) have been developed and used for investigation of the electric field (EF) extension around different types of DBS lead designs (symmetric, steering) and stimulation modes (voltage, current). The electrode surrounding was represented either with a homogeneous model or a patient-specific model based on individual preoperative magnetic resonance imaging (MRI). The EF was visualized and compared for different lead designs and operating modes.

    In Paper I, the EF was quantitatively investigated around two lead designs (3389 and 6148) simulated to operate in voltage and current mode under acute and chronic time points following implantation.Simulations showed a major impact on the EF extension between postoperative time points which may explain the clinical decisions to change the stimulation amplitude weeks after implantation. In Paper II, the simulations were expanded to include two leads having steering function (6180, Surestim1) and patient-specific FEM simulations in the zona incerta. It was found that both the heterogeneity of the tissue and the operating mode, influence the EF distribution and that equivalent contact configurations of the leads result in similar EF. The steering mode presented larger volumes in current mode when using equivalent amplitudes. Simulations comparing DBS and intraoperative stimulation test using a microelectrode recording (MER) system (Paper III), showed that several parallel MER leads and the presence of the non-active DBS contacts influence the EF distribution and that the DBS EF volume can cover, but also extend to, other anatomical areas.

    Paper IV introduces a method for an objective exploitation of intraoperative stimulation test data in order to identify the optimal implant position in the thalamus of the chronic DBS lead. Patient-specific EF simulations were related to the anatomy with the help of brain atlases and the clinical effects which were quantified by accelerometers. The first results indicate that the good clinical effect in ET is due to several structures around the ventral intermediate nucleus of the thalamus.

    List of papers
    1. Influence on Deep Brain Stimulation from Lead Design, Operating Mode and Tissue Impedance Changes – A Simulation Study
    Open this publication in new window or tab >>Influence on Deep Brain Stimulation from Lead Design, Operating Mode and Tissue Impedance Changes – A Simulation Study
    2015 (English)In: Brain Disorders and Therapy, ISSN 2168-975X, Vol. 4, no 3, article id 1000169Article in journal (Refereed) Published
    Abstract [en]

    Background: Deep brain stimulation (DBS) systems in current mode and new lead designs are recently available. To switch between DBS-systems remains complicated as clinicians may lose their reference for programming. Simulations can help increase the understanding.

    Objective: To quantitatively investigate the electric field (EF) around two lead designs simulated to operate in voltage and current mode under two time points following implantation.

    Methods: The finite element method was used to model Lead 3389 (Medtronic) and 6148 (St Jude) with homogenous surrounding grey matter and a peri-electrode space (PES) of 250 μm. The PES-impedance mimicked the acute (extracellular fluid) and chronic (fibrous tissue) time-point. Simulations at different amplitudes of voltage and current (n=236) were performed using two different contacts. Equivalent current amplitudes were extracted by matching the shape and maximum EF of the 0.2 V/mm isolevel.

    Results: The maximum EF extension at 0.2 V/mm varied between 2-5 mm with a small difference between the leads. In voltage mode EF increased about 1 mm at acute compared to the chronic PES. Current mode presented the opposite relationship. Equivalent EFs for lead 3389 at 3 V were found for 7 mA (acute) and 2.2 mA (chronic).

    Conclusions: Simulations showed a major impact on the electric field extension between postoperative time points. This may explain the clinical decisions to reprogram the amplitude weeks after implantation. Neither the EF extension nor intensity is considerably influenced by the lead design.

    Place, publisher, year, edition, pages
    Los Angeles, CA, USA: Omics Publishing Group, 2015
    Keywords
    deep brain stimulation (DBS), voltage and current stimulation, finite element method
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-120680 (URN)10.4172/2168-975X.1000169 (DOI)
    Funder
    Swedish Research Council, 621-2013-6078
    Available from: 2015-08-21 Created: 2015-08-20 Last updated: 2018-09-10Bibliographically approved
    2. Investigation into Deep Brain Stimulation Lead Designs: A Patient-Specific Simulation Study
    Open this publication in new window or tab >>Investigation into Deep Brain Stimulation Lead Designs: A Patient-Specific Simulation Study
    Show others...
    2016 (English)In: Brain Sciences, ISSN 2076-3425, E-ISSN 2076-3425, Vol. 6, no 3, p. 1-16Article in journal (Refereed) 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.

    Place, publisher, year, edition, pages
    MDPI, 2016
    Keywords
    deep brain stimulation (DBS), steering, patient-specific, electric field, finite element method, neuron model, brain model, zona incerta (ZI), electrode design
    National Category
    Medical Engineering
    Identifiers
    urn:nbn:se:liu:diva-131863 (URN)10.3390/brainsci6030039 (DOI)27618109 (PubMedID)
    Available from: 2016-10-11 Created: 2016-10-11 Last updated: 2018-09-10Bibliographically approved
    3. Electric Field Comparison between Microelectrode Recording and Deep Brain Stimulation Systems: A Simulation Study
    Open this publication in new window or tab >>Electric Field Comparison between Microelectrode Recording and Deep Brain Stimulation Systems: A Simulation Study
    Show others...
    2018 (English)In: Brain Sciences, ISSN 2076-3425, E-ISSN 2076-3425, Vol. 8, no 2Article in journal (Refereed) Published
    Abstract [en]

    The success of deep brain stimulation (DBS) relies primarily on the localization of the implanted electrode. Its final position can be chosen based on the results of intraoperative microelectrode recording (MER) and stimulation tests. The optimal position often differs from the final one selected for chronic stimulation with the DBS electrode. The aim of the study was to investigate, using finite element method (FEM) modeling and simulations, whether lead design, electrical setup, and operating modes induce differences in electric field (EF) distribution and in consequence, the clinical outcome. Finite element models of a MER system and a chronic DBS lead were developed. Simulations of the EF were performed for homogenous and patient-specific brain models to evaluate the influence of grounding (guide tube vs. stimulator case), parallel MER leads, and non-active DBS contacts. Results showed that the EF is deformed depending on the distance between the guide tube and stimulating contact. Several parallel MER leads and the presence of the non-active DBS contacts influence the EF distribution. The DBS EF volume can cover the intraoperatively produced EF, but can also extend to other anatomical areas. In conclusion, EF deformations between stimulation tests and DBS should be taken into consideration as they can alter the clinical outcome

    Place, publisher, year, edition, pages
    MDPI, 2018
    Keywords
    microelectrode recording (MER); finite element method (FEM); deep brain stimulation (DBS); brain model; Dice coefficient; patient-specific
    National Category
    Medical Engineering
    Identifiers
    urn:nbn:se:liu:diva-145112 (URN)10.3390/brainsci8020028 (DOI)
    Available from: 2018-02-12 Created: 2018-02-12 Last updated: 2018-09-10
    4. Patient-Specific Electric Field Simulations and Acceleration Measurements for Objective Analysis of Intraoperative Stimulation Tests in the Thalamus
    Open this publication in new window or tab >>Patient-Specific Electric Field Simulations and Acceleration Measurements for Objective Analysis of Intraoperative Stimulation Tests in the Thalamus
    Show others...
    2016 (English)In: Frontiers in Human Neuroscience, ISSN 1662-5161, E-ISSN 1662-5161, Vol. 10, p. 1-14, article id 577Article in journal (Refereed) Published
    Abstract [en]

    Despite an increasing use of deep brain stimulation (DBS) the fundamental mechanisms of action remain largely unknown. Simulation of electric entities has previously been proposed for chronic DBS combined with subjective symptom evaluations, but not for intraoperative stimulation tests. The present paper introduces a method for an objective exploitation of intraoperative stimulation test data to identify the optimal implant position of the chronic DBS lead by relating the electric field (EF) simulations to the patient-specific anatomy and the clinical effects quantified by accelerometry. To illustrate the feasibility of this approach, it was applied to five patients with essential tremor bilaterally implanted in the ventral intermediate nucleus (VIM). The VIM and its neighborhood structures were preoperatively outlined in 3D on white matter attenuated inversion recovery MR images. Quantitative intraoperative clinical assessments were performed using accelerometry. EF simulations (n = 272) for intraoperative stimulation test data performed along two trajectories per side were set-up using the finite element method for 143 stimulation test positions. The resulting EF isosurface of 0.2 V/mm was superimposed to the outlined anatomical structures. The percentage of volume of each structure’s overlap was calculated and related to the corresponding clinical improvement. The proposed concept has been successfully applied to the five patients. For higher clinical improvements, not only the VIM but as well other neighboring structures were covered by the EF isosurfaces. The percentage of the volumes of the VIM, of the nucleus intermediate lateral of the thalamus and the prelemniscal radiations within the prerubral field of Forel increased for clinical improvements higher than 50% compared to improvements lower than 50%. The presented new concept allows a detailed and objective analysis of a high amount of intraoperative data to identify the optimal stimulation target. First results indicate agreement with published data hypothesizing that the stimulation of other structures than the VIM might be responsible for good clinical effects in essential tremor. (Clinical trial reference number: Ref: 2011-A00774-37/AU905)

    Place, publisher, year, edition, pages
    Frontiers Research Foundation, 2016
    Keywords
    deep brain stimulation (DBS), intraoperative stimulation tests, essential tremor, acceleration measurements, finite element method (FEM) simulations, ventral intermediate nucleus (VIM), patient-specific brain maps
    National Category
    Medical Engineering
    Identifiers
    urn:nbn:se:liu:diva-132790 (URN)10.3389/fnhum.2016.00577 (DOI)000388426400001 ()
    Available from: 2016-11-25 Created: 2016-11-25 Last updated: 2018-09-10Bibliographically approved
  • 5.
    Alonso, Fabiola
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Comparison of deep brain stimulation systems2014In: Poster Presentations, 2014, Vol. 29, p. 1173-1173, article id Suppl 1Conference paper (Other academic)
    Abstract [en]

    Objective: To quantitatively compare the electric field generated by voltage and current controlled deep brain stimulation systems.

    Background: Traditionally deep brain stimulation (DBS) systems have used voltage control however more recently, current controlled systems have been approved to treat Parkinson's disease and related movement disorders. In the endeavor of understanding the behavior of DBS systems a common approach is the use of computer models suitable to simulate the electric field, current density and other related electric parameters.

    Methods: 2D finite element models based on commercially available DBS systems have been built for each system: I. Model 3389, Medtronic Inc., USA for voltage control; and II. Model 6142, St Jude Medical Inc. USA for current control. The brain tissue has been simplified to homogeneous and isotropic medium. The electric settings correspond to a monopolar configuration, using one of the four contacts available as the active electrode and the outer boundary of the tissue as the reference. Three simulations were performed to mimic different stages of the leads implantation: a) an original stage where the brain tissue is considered as pure gray matter, b) an acute stage that simulates the leakage of cerebral spinal fluid immediately after the electrodes' insertion; and c) a chronic stage mimicking fibrous tissue created around the electrodes some weeks after implantation. Both systems were submitted to the same conditions using as active electrode the third contact from the tip of the lead. The comparison is based on the maximal distance reached by the isopotential of 0.2 V/mm.

    Results: The simulations showed that voltage controlled stimulation systems are more susceptible to changes in the electrical conductivity of the medium i.e. change over time of the tissue around the electrode. This agrees with the adjustment of the stimulation amplitude often necessary a few weeks postoperatively. Current controlled stimulation in turn, presented a linear behavior of the distance reached at different stimulation amplitudes at all stages.

    Conclusions: Current controlled stimulation might be a good option due to its linear behavior over time, nevertheless more studies including a more realistic brain model, different designs of DBS electrodes and different electric parameter, are needed to encourage the use of this type of systems.

  • 6.
    Alonso, Fabiola
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Latorre, Malcolm
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Comparison of Three Deep Brain Stimulation Lead Designs under Voltage and Current Modes2015In: WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING, 2015, VOLS 1 AND 2 / [ed] David A. Jaffray, Springer, 2015, Vol. 51, p. 1196-1199Conference paper (Refereed)
    Abstract [en]

    Since the introduction of deep brain stimulation (DBS) the technique has been dominated by Medtronic sys-tems. In recent years, new DBS systems have become available for patients, and some are in clinical trials. The present study aims to evaluate three DBS leads operated in either voltage or current mode. 3D finite element method (FEM) models were built in combination with a neuron model for this purpose. The axon diameter was set to D = 5 μm and simulations performed in both voltage (0.5-5 V) and current (0.5-5 mA) mode. The evaluation was achieved based on the distance from the lead for neural activation and the electric field (EF) extension at 0.1 V/mm. The results showed that the neural activation distance agrees well between the leads with an activation distance dif-ference less than 0.5 mm. The shape of the field at the 0.1 V/mm isopotential surface in 3D is mostly spherical in shape around the activated section of the steering lead.

  • 7.
    Alonso, Fabiola
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Latorre, Malcolm
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Neural Activation Compared to Electric Field Extension of Three DBS Lead Designs2015Conference paper (Refereed)
    Abstract [en]

    SINCE the introduction of deep brain stimulation (DBS) about 20 years ago, the stimulation technique has been dominated by Medtronic DBS-system setup. In recent years, new DBS systems have become available, of which some are in clinical trials or available to patients [1]. In the present study three different lead designs are investigated via computer simulation:

    Medtronic 3389, St. Jude 6148 and Sapiens SureStim. The aim was to compare the neural activation distance and the electric field (EF) maximum spatial extension for each lead.

    A 3D finite element method model was built using COMSOL Multiphysics 4.4a (COMSOL AB, Stockholm, Sweden) to simulate the electric potential around the DBS lead. Brain tissue was modelled as a homogeneous volume of grey matter (electric conductivity of 0.09 S/m). The electrode-tissue interface was modelled with a 250μm thick peri-electrode space mimicking the fibrous tissue which covers the lead at the chronic stimulation stage (σ = 0.06S/m, equivalent to white matter electric conductivity). The stimulation amplitude was set to 1V in monopolar configuration using C1 electrode or equivalent in all cases. Each simulated electric potential distribution was exported to MatLab (The MathWorks, USA) and used as input to a cable neuron simulation.

    An axon cable model with 21 nodes based on the concept by Åström et al., [2] was set up in MatLab and combined with the exported field distributions. The model considered a 5 μm thick neuron, a pulse width of 60 μs and a drive potential ranging from 0.5 V to 5 V in 0.5 V steps.

    The SureStim lead results showed a shorter neural activation distance and EF extension. The distance to the isolevel of 0.2 V/mm is close to the neural activation distance at each stimulation amplitude, and we conclude that the electric field is a suitable predictor to visualize the stimulated regions.

  • 8.
    Angland, Erik
    et al.
    Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Karlsson, Henrik
    Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Gustafsson, Agnetha
    Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Pettersson, Håkan
    Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Luftmätningar av  inhalerat 99mTc till BMA vid ventilationsundersökningar med Technegas.2006Conference paper (Other academic)
  • 9.
    Antonsson, Jacob
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Motion Tracking Using a Permanent Magnet2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this project the possibility of using a network of magnetometers sensing a permanent magnet for tracking has been investigated. Both the orientation and the position of the magnet have been considered. A dipole approximation of the magnetic field is used to develop two models. One of the models parametrizes the orientation with the magnetic moment vector, while the other parametrizes the orientation with a unit quaternion. An extended Kalman filter have been used to estimate position and orientation.

    Several calibration algorithms have been developed to calibrate for sensor errors, differences in sensor coordinate frame orientations and also for the estimation of the magnetic moment norm of a permanent magnet. The models have been tested using an optical reference system for position and orientation estimation. Initial results are ambiguous and further testing is necessary. One conclusion is that the model using the magnetic moment vector as orientation parametrization is less sensitive to the accuracy of the initial guesses of the filter recursions and also less sensitive to possible model errors.

    A mathematical result of the possibility of using a non stationary sensor network to track the magnet is also given.

  • 10.
    Athanasiou, Vasileios
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Estimation and modelling of fMRI BOLD response2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    One of the current topics of research in neuroimaging techniques is related to explaining and modelling the Blood Oxygen Level Dependent (BOLD) responses. BOLD responses are estimated by processing functional Magnetic Resonance Imaging (fMRI) data. BOLD responses are caused by hemodynamic responses to neural activity which alter the levels of blood oxygenation at local brain regions. The main aims of the current thesis were to i) develop and examine methods regarding BOLD response estimation from the visual cortex and the frontal cortex of human brain and to ii) develop a model in order to explain the physiological mechanisms which cause the estimated BOLD responses.

    In order to satisfy the main aims, fMRI data were provided by the Center of Medical Imaging and Visualization (CMIV). The provided fMRI data consist of fMRI brain measurements of twelve healthy human subjects who were subjected to visual stimulation. By processing the fMRI data, Regions Of Interest (ROIs) were extracted at the anatomical sites of the visual cortex and the frontal cortex. Afterwards, the fMRI data were manipulated in order to extract BOLD responses from the visual cortex and the frontal cortex. Various methods were developed and compared in terms of which technique provided well representative BOLD responses.       

    Subsequently, a model was developed by using software Wolfram Mathematica 9 in order to explain the physiological mechanisms of the estimated BOLD responses at the visual and the frontal cortex. The model aimed to solve for oxygen concentration in blood plasma as blood flows from the arterial part to the venous part of the blood circulation system through a capillary. Oxygen outward diffusion through the capillary wall and oxygen concentration at the extravascular environment were modelled as well. Blood plasma oxygen concentration was turned into hemoglobin oxygen saturation (Sa ) through hemoglobin oxygen dissociation curve and Henry’s law for gases. As a result, the Sa  was estimated through modelling for oxygen concentration in blood plasma. Finally, the developed model ended to a system with input the fractional change of Cerebral Blood Flow (CBF) velocity and Cerebral Metabolic Rate of Oxygen (CMR ) and as output a proportional signal to the BOLD response. By simulating for different scenarios of fractional changes of CBF velocity and CMR  and by comparing the resulted BOLD responses to the estimated ones, it was attempted to explain for the physiological mechanisms which caused the BOLD responses at the anatomical sites of the visual and frontal cortex.

  • 11.
    Balkanyi, Laszlo
    et al.
    European Centre for Disease Prevention and Control, Stockholm, Sweden.
    Schulz, Stefan
    Medizinische Universität Graz, Austria and Freiburg University Medical Center, Freiburg, Germany.
    Cornet, Ronald
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Bodenreider, Olivier
    National Library of Medicine, Bethsheda, USA.
    Medical concept representation: the years beyond 2000.2013In: Proceedings of Studies in Health Technology & Informatics, vol. 192, IOS Press, 2013, Vol. 192, p. 1011-1011Conference paper (Refereed)
    Abstract [en]

    This work aims at understanding the state of the art in the broad contextual research area of "medical concept representation". Our data support the general understanding that the focus of research has moved toward medical ontologies, which we interpret as a paradigm shift. Both the opinion of socially active groups of researchers and changes in bibliometric data since 1988 support this opinion. Socially active researchers mention the OBO foundry, SNOMED CT, and the UMLS as anchor activities.

  • 12.
    Bleser, Gabriele
    et al.
    German Research Center for Artificial Intelligence (DFKI), Kaiserslautern, Germany.
    Steffen, Daniel
    German Research Center for Artificial Intelligence (DFKI), Kaiserslautern, Germany.
    Reiss, Attila
    ACTLab, University of Passau, 94032, Passau, Germany.
    Weber, Markus
    German Research Center for Artificial Intelligence (DFKI), Kaiserslautern, Germany.
    Hendeby, Gustaf
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Fradet, Laetitia
    Université de Poitiers, 86000, Poitiers, France.
    Personalized Physical Activity Monitoring Using Wearable Sensors2015In: Smart Health: Open Problems and Future Challenges / [ed] Andreas Holzinger, Carsten Röcker, Martina Ziefle, Springer International Publishing , 2015, p. 99-124Chapter in book (Refereed)
    Abstract [en]

    It is a well-known fact that exercising helps people improve their overall well-being; both physiological and psychological health. Regular moderate physical activity improves the risk of disease progression, improves the chances for successful rehabilitation, and lowers the levels of stress hormones. Physical fitness can be categorized in cardiovascular fitness, and muscular strength and endurance. A proper balance between aerobic activities and strength exercises are important to maximize the positive effects. This balance is not always easily obtained, so assistance tools are important. Hence, ambient assisted living (AAL) systems that support and motivate balanced training are desirable. This chapter presents methods to provide this, focusing on the methodologies and concepts implemented by the authors in the physical activity monitoring for aging people (PAMAP) platform. The chapter sets the stage for an architecture to provide personalized activity monitoring using a network of wearable sensors, mainly inertial measurement units (IMU). The main focus is then to describe how to do this in a personalizable way: (1) monitoring to provide an estimate of aerobic activities performed, for which a boosting based method to determine activity type, intensity, frequency, and duration is given; (2) supervise and coach strength activities. Here, methodologies are described for obtaining the parameters needed to provide real-time useful feedback to the user about how to exercise safely using the right technique.

  • 13.
    Budde, Kiran Kumar
    Linköping University, Department of Electrical Engineering, Computer Vision.
    A Matlab Toolbox for fMRI Data Analysis: Detection, Estimation and Brain Connectivity2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Functional Magnetic Resonance Imaging (fMRI) is one of the best techniques for neuroimaging and has revolutionized the way to understand the brain functions. It measures the changes in the blood oxygen level-dependent (BOLD) signal which is related to the neuronal activity. Complexity of the data, presence of different types of noises and the massive amount of data makes the fMRI data analysis a challenging one. It demands efficient signal processing and statistical analysis methods.  The inference of the analysis is used by the physicians, neurologists and researchers for better understanding of the brain functions.

         The purpose of this study is to design a toolbox for fMRI data analysis. It includes methods to detect the brain activity maps, estimation of the hemodynamic response (HDR) and the connectivity of the brain structures. This toolbox provides methods for detection of activated brain regions measured with Bayesian estimator. Results are compared with the conventional methods such as t-test, ordinary least squares (OLS) and weighted least squares (WLS). Brain activation and HDR are estimated with linear adaptive model and nonlinear method based on radial basis function (RBF) neural network. Nonlinear autoregressive with exogenous inputs (NARX) neural network is developed to model the dynamics of the fMRI data.  This toolbox also provides methods to brain connectivity such as functional connectivity and effective connectivity.  These methods are examined on simulated and real fMRI datasets.

  • 14.
    Cedersund, Gunnar
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Knudsen, C.
    Technical University of Denmark.
    Improved parameter estimation for systems with an experimentally located Hopf bifurcation2005In: IEE Proceedings - Systems Biology, ISSN 1741-2471, E-ISSN 1741-248X, Vol. 152, no 3, p. 161-168Article in journal (Refereed)
    Abstract [en]

    When performing system identification, we have two sources of information: experimental data and prior knowledge. Many cell-biological systems are oscillating, and sometimes we know an input where the system reaches a Hopf bifurcation. This is the case, for example, for glycolysis in yeast cells and for the Belousov-Zhabotinsky reaction, and for both of these systems there exist significant numbers of quenching data, ideal for system identification. We present a method that includes prior knowledge of the location of a Hopf bifurcation in estimation based on time-series. The main contribution is a reformulation of the prior knowledge into the standard formulation of a constrained optimisation problem. This formulation allows for any of the standard methods to be applied, including all the theories regarding the methods properties. The reformulation is carried out through an over-parametrisation of the original problem. The over-parametrisation allows for extra constraints to be formed, and the net effect is a reduction of the search space. A method that can solve the new formulation of the problem is presented, and the advantage of adding the prior knowledge is demonstrated on the Brusselator.

  • 15.
    Cervin, Ida
    et al.
    Sectra AB, Chalmers University of Technology, Sectra AB, Gothenburg, Sweden.
    Molin, Jesper
    Center for Medical Image Science and Visualization, Chalmers University of Technology, Sectra AB, Gothenburg, Sweden.
    Lundström, Claes
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Improving the creation and reporting of structured findings during digital pathology review2016In: Journal of Pathology Informatics, ISSN 2229-5089, E-ISSN 2153-3539, Vol. 7, no 1, p. 32-32Article in journal (Refereed)
    Abstract [en]

    Background: Today, pathology reporting consists of many separate tasks, carried out by multiple people. Common tasks include dictation during case review, transcription, verification of the transcription, report distribution, and report the key findings to follow-up registries. Introduction of digital workstations makes it possible to remove some of these tasks and simplify others. This study describes the work presented at the Nordic Symposium on Digital Pathology 2015, in Linköping, Sweden. Methods: We explored the possibility to have a digital tool that simplifies image review by assisting note-taking, and with minimal extra effort, populates a structured report. Thus, our prototype sees reporting as an activity interleaved with image review rather than a separate final step. We created an interface to collect, sort, and display findings for the most common reporting needs, such as tumor size, grading, and scoring. Results: The interface was designed to reduce the need to retain partial findings in the head or on paper, while at the same time be structured enough to support automatic extraction of key findings for follow-up registry reporting. The final prototype was evaluated with two pathologists, diagnosing complicated partial mastectomy cases. The pathologists experienced that the prototype aided them during the review and that it created a better overall workflow. Conclusions: These results show that it is feasible to simplify the reporting tasks in a way that is not distracting, while at the same time being able to automatically extract the key findings. This simplification is possible due to the realization that the structured format needed for automatic extraction of data can be used to offload the pathologists' working memory during the diagnostic review.

  • 16.
    Cornet, Ronald
    et al.
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Dentler, Kathrin
    Dept. of Computer Science, VU University Amsterdam, The Netherlands and Dept. of Medical Informatics, Academic Medical Center, University of Amsterdam, The Netherlands.
    Redundant Elements in SNOMED CT Concept Definitions2013In: proceedings of AIME 2013, Lecture Notes in ComputerScience 2013, Vol. 7885 / [ed] Peek, Niels, Marín Morales, Roque Luis, Peleg, Mor, Springer , 2013, p. 186-195Conference paper (Refereed)
    Abstract [en]

    While redundant elements in SNOMED CT concept definitions are harmless from a logical point of view, they unnecessarily make concept definitions of typically large ontologies such as SNOMED CT hard to construct and to maintain. In this paper, we apply a fully automated method to detect intra-axiom redundancies in SNOMED CT. We systematically analyse the completeness and soundness of the results of our method by examining the identified redundant elements. In absence of a gold standard, we check whether our method identifies concepts that are likely to contain redundant elements because they become equivalent to their stated subsumer when they are replaced by a fully defined concept with the same definition. To evaluate soundness, we remove all identified redundancies, and test whether the logical closure is preserved by comparing the concept hierarchy to the one of the official SNOMED CT distribution. We found that 35,010 of the 296,433 SNOMED CT concepts (12%) contain redundant elements in their definitions, and that the results of our method are sound and complete with respect to our partial evaluation. We recommend to free the stated form from these redundancies. In future, knowledge modellers should be supported by being pointed to newly introduced redundancies.

  • 17.
    Cornet, Ronald
    et al.
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology. University of Amsterdam, The Netherlands.
    Nyström, Mikael
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Karlsson, Daniel
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Medical Informatics.
    User-Directed Coordination in SNOMED CT2013In: MedInfo 2013: Proceedings of the 14th World Congress on Medical and Health Informatics / [ed] Lehmann, C.U., Ammenwerth, E., Nøhr, C., Amsterdam: IOS Press, 2013, p. 72-76Conference paper (Refereed)
    Abstract [en]

    The possibility of post-coordination of SNOMED CT concepts, especially by clinical users, is both an asset and a challenge for SNOMED CT implementation. To get insight in the applicability of post-coordination, we analyzed scenarios for user-directed coordination that are described in the documentation of SNOMED CT. The analyses were based on experiences from previous and ongoing research and implementation work, including national mapping projects, and investigations on collection of data for multiple uses. These scenarios show various usability and representation problems: high number of relationships for refinement and qualification, improper options for refinement, incorrect formal definitions, and lack of support for applying editorial rules. Improved user-directed coordination in SNOMED CT in real practice requires advanced sanctioning, increased consistency of definitions of concepts in SNOMED CT, and real-time analysis of the post-coordinate expression.

  • 18.
    Cubo, Ruben
    et al.
    Uppsala University, Sweden.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. Medtron Eindhoven Design Centre, Netherlands.
    Medvedev, Alexander
    Uppsala University, Sweden.
    Electric Field Modeling and Spatial Control in Deep Brain Stimulation2015In: 2015 54TH IEEE CONFERENCE ON DECISION AND CONTROL (CDC), IEEE , 2015, p. 3846-3851Conference paper (Refereed)
    Abstract [en]

    Deep Brain Stimulation (DBS) is an established treatment, in e.g. Parkinsons Disease, whose underlying biological mechanisms are unknown. In DBS, electrical stimulation is delivered through electrodes surgically implanted into certain regions of the brain of the patient. Mathematical models aiming at a better understanding of DBS and optimization of its therapeutical effect through the simulation of the electrical field propagating in the brain tissue have been developed in the past decade. The contribution of the present study is twofold: First, an analytical approximation of the electric field produced by an emitting contact is suggested and compared to the numerical solution given by a Finite Element Method (FEM) solver. Second, the optimal stimulation settings are evaluated by fitting the field distribution to a target one to control the spread of the stimulation. Optimization results are compared to those of a geometric approach, maximizing the intersection between the target and the activated volume in the brain tissue and reducing the stimulated area beyond said target. Both methods exhibit similar performance with respect to the optimal stimuli, with the electric field control approach being faster and more versatile.

  • 19.
    Dentler, Kathrin
    et al.
    Dept. of Computer Science, VU University Amsterdam, The Netherlands and Dept. of Medical Informatics, Academic Medical Center, University of Amsterdam, The Netherlands.
    Ten Teije, Annette
    Dept. of Computer Science, VU University Amsterdam, The Netherlands.
    de Keizer, Nicolette
    Dept. of Medical Informatics, Academic Medical Center, University of Amsterdam, The Netherlands.
    Cornet, Ronald
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Barriers to the reuse of routinely recorded clinical data: a field report2013In: Proceedings of Studies in Health Technology & Informatics, vol.192, IOS Press, 2013, Vol. 192, p. 313-317Conference paper (Refereed)
    Abstract [en]

    Today, clinical data is routinely recorded in vast amounts, but its reuse can be challenging. A secondary use that should ideally be based on previously collected clinical data is the computation of clinical quality indicators. In the present study, we attempted to retrieve all data from our hospital that is required to compute a set of quality indicators in the domain of colorectal cancer surgery. We categorised the barriers that we encountered in the scope of this project according to an existing framework, and provide recommendations on how to prevent or surmount these barriers. Assuming that our case is not unique, these recommendations might be applicable for the design, evaluation and optimisation of Electronic Health Records.

  • 20.
    Diczfalusy, Elin
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Andersson, Mats
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    A diffusion tensor-based finite element model of microdialysis in the deep brain2015In: Computer Methods in Biomechanics and Biomedical Engineering, ISSN 1025-5842, E-ISSN 1476-8259, Vol. 18, no 2, p. 201-212Article in journal (Refereed)
    Abstract [en]

    Microdialysis of the basal ganglia was recently used to study neurotransmitter levels in relation to deep brain stimulation. In order to estimate the anatomical origin of the obtained data, the maximum tissue volume of influence (TVImax) for a microdialysis catheter was simulated using the finite element method. This study investigates the impact of brain heterogeneity and anisotropy on the TVImax using diffusion tensor imaging (DTI) to create a second-order tensor model of the basal ganglia. Descriptive statistics showed that the maximum migration distance for neurotransmitters varied by up to 55% (n = 98,444) for DTI-based simulations compared with an isotropic reference model, and the anisotropy differed between different targets in accordance with theory. The size of the TVImax was relevant in relation to the size of the anatomical structures of interest, and local tissue properties should be accounted for when relating microdialysis data to their anatomical targets.

  • 21.
    Diczfalusy, Elin
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Simulation of Deep Brain Stimulation for Tourette's Syndrome (oral)2011Conference paper (Refereed)
  • 22.
    Diczfalusy, Elin
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Åström, Mattias
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Software for Patient Specific Modeling and Simulation of Deep Brain Stimulation (poster)2011Conference paper (Refereed)
  • 23.
    Dieterich, Angela V.
    et al.
    University of Medical Centre, Germany.
    Botter, Alberto
    Politecn Torino, Italy.
    Martins Vieira, Taian
    Politecn Torino, Italy; University of Federal Rio de Janeiro, Brazil.
    Peolsson, Anneli
    Linköping University, Department of Medical and Health Sciences, Division of Physiotherapy. Linköping University, Faculty of Medicine and Health Sciences.
    Petzke, Frank
    University of Medical Centre, Germany.
    Davey, Paul
    Curtin University, Australia.
    Falla, Deborah
    University of Birmingham, England.
    Spatial variation and inconsistency between estimates of onset of muscle activation from EMG and ultrasound2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 42011Article in journal (Refereed)
    Abstract [en]

    Delayed onset of muscle activation can be a descriptor of impaired motor control. Activation onset can be estimated from electromyography (EMG)-registered muscle excitation and from ultrasound-registered muscle motion, which enables non-invasive measurements in deep muscles. However, in voluntary activation, EMG-and ultrasound-detected activation onsets may not correspond. To evaluate this, ten healthy men performed isometric elbow flexion at 20% to 70% of their maximal force. Utilising a multi-channel electrode transparent to ultrasound, EMG and M(otion)-mode ultrasound were recorded simultaneously over the biceps brachii muscle. The time intervals between automated and visually estimated activation onsets were correlated with the regional variation of EMG and muscle motion onset, contraction level and speed. Automated and visual onsets indicated variable time intervals between EMG-and motion onset, median (interquartile range) 96 (121) ms and 48 (72) ms, respectively. In 17% (computed analysis) or 23% (visual analysis) of trials, motion onset was detected before local EMG onset. Multi-channel EMG and M-mode ultrasound revealed regional differences in activation onset, which decreased with higher contraction speed (Spearman rho amp;gt;= 0.45, P amp;lt; 0.001). In voluntary activation the heterogeneous motor unit recruitment together with immediate motion transmission may explain the high variation of the time intervals between local EMG-and ultrasound-detected activation onset.

  • 24.
    Ghaffari, Ghazaleh
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Estimation of Stapedius-Muscle Activation using Ear Canal Absorbance Measurements: An Application of Signal Processing in Physiological Acoustics2013Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    The stapedius muscle, which is located in the middle ear, goes into contraction when the ear is exposed to high sound intensities. This muscle activation is called ‘the acoustic reflex’. Measurement of the acoustic reflex is clinically of importance since it can reveal diagnostic information about the middle ear’s pathologies. Moreover, this muscle-activation alters the acoustic characteristics of the middle ear (i.e. the acoustic impedance and the power reflectance), which in turn, can significantly manipulate one’s perception of sounds. In the present study, these acoustic characteristics are measured in the ear canal by means of absorbance measures using equivalent Thevenin circuit theory. The quantities are then compared to form the shift responses between the baseline (before the activation) and the post-activator effect. This project investigates the shifts in power reflectance and admittance of the middle ear caused by the stapedius-muscle contraction. The wideband characterization (0.1- 8 kHz) of these acoustic reflex-induced shifts is achieved using chirp signals as a probe and through ipsilateral broadband noise activator. The data acquisition and signal processing of the project are carried out using MATLAB software. The hardware consists of National Instruments USB-6212 data acquisition interface and low noise microphone system Etymotic Research ER-10B+. A group of 10 adults including 5 males and 5 females are recruited as the participants for the project. The measurements of the reflectance shifts indicate that the most robust frequency region affected by the acoustic reflex is up to 4 kHz whereas for the admittance shifts, this region is up to 2 kHz. In addition, it is shown that the stapedius-muscle contraction leads to the attenuation of the lowfrequency transmission into the middle ear (less than 1 kHz) consistent with a stiffnesscontrolled system in this range of frequencies. In contrast, the results imply that the activation of the stapedius muscle leads to a slight enhancement of the frequency transmission in the range of 1-4 kHz (corresponding to the speech frequency band). These findings suggest a beneficial role for the stapedius-muscle contraction in the perception of speech during vocalization. Furthermore, the implemented methods in this project  can be useful in better understanding the effect of the stapedius-muscle contraction on the speech perception both in normal hearing and hearing impaired persons.

  • 25.
    Glasin, Joakim
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Drug Research. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Local Health Care Services in Central Östergötland, Department of Emergency Medicine.
    Henricson, Joakim
    Linköping University, Department of Medical and Health Sciences, Division of Drug Research. Region Östergötland, Heart and Medicine Center, Department of Dermatology and Venerology. Linköping University, Faculty of Medicine and Health Sciences.
    Lindberg, Lars-Göran
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Björk Wilhelms, Daniel
    Linköping University, Department of Medical and Health Sciences, Division of Drug Research. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Local Health Care Services in Central Östergötland, Department of Emergency Medicine.
    Wireless vitals: Proof of concept for wireless patient monitoring in an emergency department setting2019In: Journal of Biophotonics, ISSN 1864-063X, E-ISSN 1864-0648, Vol. 12, no 4, article id e201800275Article in journal (Refereed)
    Abstract [en]

    Vital sign assessment is a common task in emergency medicine, but resources for continuous monitoring are restricted, data is often recorded manually, and entangled wires cause frustration. Therefore, we designed a small, wireless photoplethysmographic device capable of continuously assessing pulse, respiratory frequency and oxygen saturation on the sternum and tested the performance and feasibility in an emergency department setting. Fifty (56.3 20.2 years), consenting emergency patients (29 male) were recruited. Heart rate, respiratory rate and oxygen saturation were recorded simultaneously using the device and standard monitoring equipment. Data was compared using Bland-Altman plotting (heart rate, respiratory rate) and mean difference (oxygen saturation). The bias for heart- and respiratory rate was 0.4 (limits of agreements -11.3, 12.2 and -6.1, 7.0). Mean difference for oxygen saturation was -0.21 +/- 2.35%. This may be the first wireless device to use photoplethysmography on the sternum for vital sign assessment. We noted good agreement with standard monitors, but lack of standardization in data processing between monitoring systems may limit the generalizability of these findings. Although further improvements are needed, the feasibility of this approach provides proof of concept for a new paradigm of large scale, wireless patient monitoring.

  • 26.
    Gollvik, Martin
    Linköping University, Department of Biomedical Engineering.
    Metamodeling for ultra-fast parameter estimation: Theory and evaluation of use in real-time diagnosis of diffuse liver disease2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Diffuse liver disease is a growing problem and a major cause of death worldwide. In the final stages the treatment often involves liver resection or transplant and in deciding what course of action is to be taken it is crucial to have a correct assessment of the function of the liver. The current “gold standard” for this assessment is to take a liver biopsy which has a number of disadvantages. As an alternative, a method involving magnetic resonance imaging and mechanistic modeling of the liver has been developed at Linköping University. One of the obstacles for this method to overcome in order to reach clinical implementation is the speed of the parameter estimation. In this project the methodology of metamodeling is tested as a possible solution to this speed problem. Metamodeling involve making models of models using extensive model simulations and mathematical tools. With the use of regression methods, clustering algorithms, and optimization, different methods for parameter estimation have been evaluated. The results show that several, but not all, of the parameters could be accurately estimated using metamodeling and that metamodeling could be a highly useful tool when modeling biological systems. With further development, metamodeling could bring this non-invasive method for estimation of liver function a major step closer to application in the clinic.

  • 27.
    Grip, Helena
    et al.
    Department of Biomedical Engineering and Informatics, University Hospital, Umeå, Sweden.
    Öhberg, Fredrik
    Department of Biomedical Engineering and Informatics, University Hospital, Umeå, Sweden.
    Wiklund, Urban
    Department of Biomedical Engineering and Informatics, University Hospital, Umeå, Sweden.
    Sterner, Ylva
    Community Medicine and Rehabilitation, University Hospital, Umeå, Sweden.
    Karlsson, J. Stefan
    Department of Biomedical Engineering and Informatics, University Hospital, Umeå, Sweden.
    Gerdle, Björn
    Linköping University, Department of Clinical and Experimental Medicine, Rehabilitation Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medicine, Pain and Rehabilitation Centre.
    Classification of Neck Movement Patterns Related to Whiplash-Associated Disorders Using Neural Networks2003In: IEEE transactions on information technology in biomedicine, ISSN 1089-7771, E-ISSN 1558-0032, Vol. 7, no 4, p. 412-418Article in journal (Refereed)
    Abstract [en]

    This paper presents a new method for classification of neck movement patterns related to Whiplash-associated disorders (WAD) using a resilient backpropagation neural network (BPNN). WAD are a common diagnosis after neck trauma, typically caused by rear-end car accidents. Since physical injuries seldom are found with present imaging techniques, the diagnosis can be difficult to make. The active range of the neck is often visually inspected in patients with neck pain, but this is a subjective measure, and a more objective decision support system, that gives a reliable and more detailed analysis of neck movement pattern, is needed. The objective of this study was to evaluate the predictive ability of a BPNN, using neck movement variables as input. Three-dimensional (3-D) neck movement data from 59 subjects with WAD and 56 control subjects were collected with a ProReflex system. Rotation angle and angle velocity were calculated using the instantaneous helical axis method and motion variables were extracted. A principal component analysis was performed in order to reduce data and improve the BPNN performance. BPNNs with six hidden nodes had a predictivity of 0.89, a sensitivity of 0.90 and a specificity of 0.88, which are very promising results. This shows that neck movement analysis combined with a neural network could build the basis of a decision support system for classifying suspected WAD, even though further evaluation of the method is needed.

  • 28.
    Haj Hosseini, Neda
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Richter, Johan
    Östergötlands Läns Landsting, Reconstruction Centre, Department of Neurosurgery UHL. Linköping University, Department of Biomedical Engineering. Linköping University, Faculty of Medicine and Health Sciences.
    Milos, Peter
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery. Neurokirurgi.
    Hallbeck, Martin
    Linköping University, Department of Clinical and Experimental Medicine, Divison of Neurobiology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Clinical Pathology and Clinical Genetics.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Optical Guidance for Brain Tumor Stereotactic Biopsy2017Conference paper (Refereed)
  • 29.
    Haj-Hosseini, Neda
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Optical Coherence Tomography for 3D Cancer Imaging2015Conference paper (Refereed)
    Abstract [en]

    Optical coherence tomography (OCT) is an advanced optical imaging technology for imaging material based on their optical scattering properties. OCT provides high-resolution 2D (en face or cross-sectional) and 3D images from the surface and subsurface tissue microstructures within a few mm depth. The first article on OCT was published in 1991 by D. Huang et. al. [1]. More than 15000 articles have been published since 1991 on different applications of OCT. However, the technique has so far entered the clinical routine only within ophthalmology and cardiovascular imaging in which the majority of the articles have been published [2]. OCT is a capable technology with great potentials for further translational research and implementation in additional clinical fields. One potential application of OCT is within cancer detection intraoperatively or post operatively for providing an on-site fast diagnosis. In this study, OCT’s ability to differentiate histology and pathology for application in tissue identification, pathological diagnosis and cancer staging was investigated.

    Material and Method:

    The technology uses near infrared or infrared light for imaging tissue structures that havedifferent optical scattering properties. The technique is based on low coherence interferometryand measures the backscattered light from the tissue. The scanning dimensions and resolutions are dependent on the type of the OCT system. In this study a TELESTO IITM system (Thorlabs, Inc., NJ, USA) was used. The maximum lateral and axial resolution of the system were 13 and 5.5 μm, respectively. A total of eleven patients undergoing brain, thyroid and parathyroid surgery were included in the study.

    Results:

    Figure 1 shows a 3D scan of the fingertip taken by the described OCT system as an example. The skin layers (epidermis and dermis) including the fingerprint and a sweat gland (the spiral structure) are visible. Various tissue type specimens involved in thyroid and parathyroid surgeries and brain tumor surgery were evaluated.

  • 30.
    Haj-Hosseini, Neda
    et al.
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Gimm, Oliver
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Surgery in Linköping.
    Höög, Anders
    Linköping University, Department of Clinical and Experimental Medicine, Divison of Neurobiology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Clinical Pathology and Clinical Genetics.
    Johansson, Kenth
    Landstinget i Kalmar län och Sahlgrenska universitetssjukhus, Västra Götalandsregion.
    Optiska metoder för identifiering av bisköldkörtel och sköldkörtel2017Conference paper (Refereed)
    Abstract [sv]

    Identifiering av bisköldkörtlar är viktigt vid sköldkörtel- och bisköldkörtelkirurgi och kan vara svårt då de liknar omgivande vävnad såsom fett och lymfkörtlar. Peroperativ detektering av dessa vävnader kan förbättra möjligheten att bota patienter med hyperparathyroidism och minska risken för bisköldkörtelskador vid thyroideakirurgi. Optiska metoder är potentiella tekniker för att möjliggöra detta. Optiska tekniker utvärderades på vävnadsprover från patienter vid bisköldkörtel- och sköldkörteloperation. Teknikerna bestod av nära infraröd fluorescens (NIR) spektroskopi och optisk koherenstomografi (OCT) som ger en bild av vävnadens mikrostruktur liknande till ultraljud med högre upplösning (10 μm).

  • 31.
    Haj-Hosseini, Neda
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Milos, Peter
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Hildesjö, Camilla
    Linköping University, Department of Clinical and Experimental Medicine, Division of Clinical Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Clinical Pathology and Clinical Genetics.
    Hallbeck, Martin
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Clinical Pathology and Clinical Genetics.
    Richter, Johan
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Fluorescence spectroscopy and optical coherence tomography for brain tumor detection2016Conference paper (Refereed)
    Abstract [en]

    Resection of brain tumor is a challenging task as the tumor does not have clear borders and the malignant types specifically have often a diffuse and infiltrative pattern of growth. Recently, neurosurgical microscopes have been modified to incorporate fluorescence modules for detection of tumor when 5-aminolevulinic acid (5-ALA) is used as a contrast. We have in combination with the fluorescence microscopes implemented and evaluated a fluorescence spectroscopy based handheld probe for detecting the 5-aminolevulinic acid (ALA) induced protoporphyrin IX (PpIX) in the gliomas in 50 patients intraoperatively. The results show a significantly high sensitivity for differentiating tumor from the healthy tissue and distinguished fluorescence intensity levels in the tumor cell infiltration zone around the tumor. However, knowledge on association of the quantified fluorescence signals specifically in the intermediate inflammatory zone with the infiltrative tumor cells can be complemented with volumetric tissue imaging and a higher precision histopathological analysis. In this work, a spectral domain optical coherence tomography (OCT) system with central wavelength of 1325nm has been used to image the tissue volume that the fluorescence is collected from and is evaluated against histopathological analysis for a higher precision slicing. The results show that although healthy brain has a homogenous microstructure in the OCT images, the brain tumor shows a distinguished texture in the images correlated with the PpIX fluorescence intensity and histopathology.

  • 32.
    Haj-Hosseini, Neda
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Milos, Peter
    Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Surgery in Linköping.
    Richter, Johan
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Hildesjö, Camilla
    Linköping University, Department of Clinical and Experimental Medicine, Division of Clinical Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Hallbeck, Martin
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Clinical Pathology and Clinical Genetics.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Detection of brain tumor using fluorescence and optical coherence tomography2015Conference paper (Refereed)
    Abstract [en]

    Resection of brain tumor is a challenging task as the tumor does not have clear borders and the malignant types specifically have often a diffuse and infiltrative pattern of growth. We have previously implemented and evaluated a fluorescence spectroscopy based handheld probe for detecting the 5-aminolevulinic acid induced protoporphyrin IX (PpIX) in the gliomas. To add another dimension to the brain tumor detection and volumetric analysis of the tissue that exhibits fluorescence, optical coherence tomography was investigated on tumor specimens.

    Material and Methods:

    A fluorescence microscopy and a spectroscopy system as reported previously were used for detecting the fluorescence signals [1, 2]. A total of 50 patients have been included for intraoperative assessment of the tumor borders using the fluorescence techniques. A spectral domain OCT imaging system (TELESTO II, Thorlabs, Inc., NJ, USA) with central wavelength of 1325 nm was used to study the tissue microstructure post operatively. The system has a resolution of 13 and 5.5 μm in the lateral and axial directions, respectively. Tissue specimens from three patients undergoing brain tumor surgery were studied using the OCT system.

    Results and Conclusion:

    Using fluorescence spectroscopy the tumor could be detected with a sensitivity of 0.84 which was significantly higher than that of the surgical microscope (0.30). Brain tissue appeared rather homogeneous in the OCT images however the highly malignant tissue showed a clear structural difference from the non-malignant or low malignant brain tumor tissue which could be related to the fluorescence signal intensities.

  • 33.
    Haj-Hosseini, Neda
    et al.
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Richter, Johan
    Linköping University, Department of Biomedical Engineering. Linköping University, Faculty of Science & Engineering. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Hallbeck, Martin
    Linköping University, Department of Clinical and Experimental Medicine, Divison of Neurobiology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Clinical pathology.
    Milos, Peter
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Stereotactic Brain Tumor Optical Biopsy2018Conference paper (Other academic)
    Abstract [en]

    To provide guidance for targeting diagnostic tumor tissue and to avoid vessel rupture during the biopsy procedure an application specific fiber optic probe was devel-oped. The setup incorporated an in-house developed fluorescence spectroscopy system for 5-aminolevulinic acid (5-ALA) induced protopophyrin IX (PpIX) for detection in the tumor, and laser Doppler flowmeter (LDF) system for measurement of blood perfusion. Fluorescence and blood flow were recorded millimeter-wise towards the pre-calculated target. In conclusion, the optical probe made real-time detection of tumor possible and has a potential for vessel detection during the biopsy procedures. Moreover, the PpIX fluorescence, autofluorescence and blood flow in the tumor could be studied at precise positions in the brain and the tumor. In the next step, further anal-ysis will be added.

  • 34.
    Haj-Hosseini, Neda
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Richter, Johan
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Hallbeck, Martin
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Clinical Pathology and Clinical Genetics.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Low dose 5-aminolevulinic acid: Implications in spectroscopic measurements during brain tumor surgery2015In: Photodiagnosis and Photodynamic Therapy, ISSN 1572-1000, E-ISSN 1873-1597, Vol. 12, no 2, p. 209-214Article in journal (Refereed)
    Abstract [en]

    Background

    Using 5-aminolevulinic acid (ALA) as an intraoperative fluorescence contrast has been proven to improve the resection of glioblastoma and contribute to prolonged patient survival. ALA accumulates as protoporphyrin IX (PpIX) in the tumor cells and is administered in an advised dose of 20 mg/kg body weight (b.w.) for brain tumor resection using fluorescence surgical microscopes. PpIX fluorescence availability and intensities of a four folds lower ALA dose (5 mg/kg b.w.) has been investigated in glioblastomas and skin using a spectroscopy system adapted for surgical guidance.

    Methods

    A total of 30 adult patients diagnosed with high grade gliomas were included in the analysis. ALA was orally administered in doses of 5 mg/kg b.w. (n = 15) dissolved in orange juice or 20 mg/kg b.w. (n = 15) dissolved in water. A fluorescence spectroscopy system with a handheld fiber-optical probe was used for performing the quantitative fluorescence measurements.

    Results

    The binominal comparison of the diagnostic performance parameters showed no significant statistical difference (p > 0.05). The median fluorescence values in tumor were 2-3 times higher for the high ALA dose group. No PpIX was detected in the skin of the patients in the low dose group (0/4) while PpIX was detected in the skin of the majority of the patients in the high ALA dose group (13/14).

    Conclusions

    Application of 5 mg/kg ALA was evaluated as equally reliable as the higher dose regarding the diagnostic performance when guidance was performed using a spectroscopic system. Moreover, no PpIX was detected in the skin of the patients.

  • 35.
    Haj-Hosseini, Neda
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Medicine and Health Sciences.
    Richter, Johan
    Linköping University, Department of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Milos, Peter
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Hallbeck, Martin
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Clinical Pathology and Clinical Genetics.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Optical guidance for stereotactic brain tumor biopsy procedures-preliminary clinical evaluation2017Conference paper (Refereed)
    Abstract [en]

    During stereotactic biopsy on suspected tumors in the brain, tissue samples are harvested to determine the malignancy. To provide guidance for finding the diagnostic tumor sites and to avoid vessel rupture, an application specific probe was developed. The setup incorporated spectroscopy for detection of 5-aminolevulinic acid induced protoporphyrin (PpIX) fluorescence and blood flow using laser Doppler flowmetry. The PpIX fluorescence was significantly different in the tumor compared to the gliotic marginal zone (p < 0.05). In conclusion, the systems made real-time tumor detection and vessel tracking possible. Moreover, the autofluorescence and blood perfusion could be studied in the tumor.

  • 36.
    Haj-Hosseini, Neda
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Medicine and Health Sciences.
    Richter, Johan
    Linköping University, Department of Biomedical Engineering. Linköping University, Faculty of Medicine and Health Sciences.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Photodiagnostics in Brain Tumor Surgery2014In: Medicinteknikdagarna, Göteborg, 14-16 oktober, 2014: Sammanfattningar, Göteborg: Svensk förening för medicinsk teknik och fysik , 2014Conference paper (Refereed)
    Abstract [en]

    Since getting approved for clinical application in neurosurgery 5-aminolevulinic acid (ALA), that is a fluorescence contrast agent, has attracted the interest of many neurosurgical clinics to implement it in their surgical routine. ALA naturally exists in the body and the external administration of the substance induces accumulation of a fluorophore known as protoporphyrin IX (PpIX) in the malignant cells due to a broken blood brain barrier and the altered enzyme levels in the brain tumor. The detection and visualization of PpIX in the clinical routine is conventionally performed using a modified neuro surgical microscope. As a complementary technique for detection of ALA-induced fluorescence and to perform objective and quantitative measurements, our group has developed a spectroscopy system adapted to the equipment in the operating room. The system includes a hand-held fiber optic probe which can be integrated in the neuronavigation and stereotactic systems. The main advantages of the system are the ease of use, high sensitivity, quantitative fluorescence detection and the possibility of applying a low dose of fluorescence contrast agent while obtaining equally reliable results as with the high dose. In this contribution we present our experience, gains and challenges from implementation of the system during brain tumor surgery in forty adult patients. The methods and systems are currently being adapted for implementation during operations of pediatric brain tumors.

  • 37.
    Haj-Hosseini, Neda
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Health Sciences.
    Richter, Johan
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Quantitative ALA photodiagnostics in Neurosurgery2014Conference paper (Other academic)
  • 38.
    Haj-Hosseini, Neda
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Salerud, Göran
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Compensation of blood interference in fiber-optical based fluorescence guided resection of brain tumor2011Conference paper (Refereed)
  • 39.
    Haj-Hosseini, Neda
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Stepp, Herbert
    Ludwig Maximilians Universitet, München.
    Markwardt, Niklas
    Ludwig Maximilians Universitet, München.
    Gimm, Oliver
    Linköping University, Department of Clinical and Experimental Medicine, Division of Clinical Sciences. Linköping University, Faculty of Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Surgery in Linköping.
    Shabo, Ivan
    Linköping University, Department of Clinical and Experimental Medicine, Division of Clinical Sciences. Linköping University, Faculty of Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Surgery in Linköping.
    Optical biopsy during thyroid and parathyroid surgery2015Conference paper (Refereed)
  • 40.
    Haj-Hosseini, Neda
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Optical Coherence Tomography as a Future Modality in Digital Pathology2015Conference paper (Other academic)
  • 41.
    Hemm, Simone
    et al.
    Institute for Medical and Analytical Technologies (IMA), FHNW, Switzerland.
    Richter, Johan C.O.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology. Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Zsigmond, Peter
    Linköping University, Department of Clinical and Experimental Medicine, Neurosurgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Optical measurements for guidance during deep brain stimulation implantation2011Conference paper (Refereed)
  • 42.
    Hemm-Ode, Simone
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology. Institute for Medical and Analytical Technologies, University of Applied Sciences and Art Northwestern Switzerland, Basel.
    Patient-specific electric field simulations and acceleration measurements for intraoperative test-stimulations2014Conference paper (Other academic)
  • 43.
    Henzler, Philipp
    et al.
    Ulm University, Ulm, Germany.
    Rasche, Volker
    Ulm University, Ulm, Germany.
    Ropinski, Timo
    Ulm University, Ulm, Germany.
    Ritschel, Tobias
    University College London, London, United Kingdom.
    Single-image Tomography: 3D Volumes from 2D Cranial X-Rays2018In: Computer Graphics Forum (Proceedings of Eurographics 2018), Vol. 37, no 2, p. 377-388Article in journal (Refereed)
    Abstract [en]

    As many different 3D volumes could produce the same 2D x‐ray image, inverting this process is challenging. We show that recent deep learning‐based convolutional neural networks can solve this task. As the main challenge in learning is the sheer amount of data created when extending the 2D image into a 3D volume, we suggest firstly to learn a coarse, fixed‐resolution volume which is then fused in a second step with the input x‐ray into a high‐resolution volume. To train and validate our approach we introduce a new dataset that comprises of close to half a million computer‐simulated 2D x‐ray images of 3D volumes scanned from 175 mammalian species. Future applications of our approach include stereoscopic rendering of legacy x‐ray images, re‐rendering of x‐rays including changes of illumination, view pose or geometry. Our evaluation includes comparison to previous tomography work, previous learning methods using our data, a user study and application to a set of real x‐rays.

  • 44.
    Hult, Peter
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    NovaMedTech – Innovationer för morgondagens vård genom samverkan med vård, akademi och industri2010Conference paper (Other (popular science, discussion, etc.))
    Abstract [sv]

    Med en kraftig ökning av andelen äldre i befolkningen ställs allt större krav på sjukvården. Ny medicinsk teknik utgör en möjlig väg att göra vården effektivare. Utgående från detta är NovaMedTech en innovativ miljö som stöds av EUs Strukturfond och som skall bidra till att stärka ny utveckling av medicinsk teknik inom regionen Östra Mellansverige dvs de fyra länen Sörmland, Västmanland, Örebro och Östergötland. I programmet tas ett samlat grepp genom att vård, akademi och industri samverkar mellan de olika länen. Satsningen stärks av länens kompletterande styrkor.

    NovaMedTech satsar genom ekonomiskt stöd från EU-strukturfondsprogram via Tillväxtverket på de två olika produktområden: Medicinsk teknik för distribuerad vård och personlig hälsa och Medicinsk teknik för bildbaserad diagnostik och terapi. Vi stöder ett 30-tal konkreta projekt mot klinisk testning och kommersialisering av produkter och tjänster.

    Genom NovaMedTech utvecklas även en innovativ miljö där ett brett nätverk har skapats och där dess aktörer har givits möjlighet att samverka, utbyta erfarenheter, identifiera nya idéer mm. Viktiga framgångsfaktorer för NovaMedTech har varit en god regional förankring, en mångfald av aktörer inom vård, akademi och näringsliv, att satsningen bygger på redan befintliga utvecklingsstrukturer i form av nätverk, innovationsstöd, inkubatorverksamhet, nyföretagarstöd, såddfinansiering, hälsoekonomisk analys och entreprenörskapssatsningar mm, samt att NovaMedTech har en stark koppling till näringslivet.

    Produktområdet Medicinsk teknik för distribuerad vård och personlig hälsa handlar om teknik för fysiologisk övervakning av patienter i hemmiljö samt teknik för diagnostik inom närvård/primärvård. I framtiden bör patientinformation och mätdata överföras istället för att patienter transporteras. Lösningar kan innefatta teknik för ”point of care”-diagnostik inom närvård/primärvård. Med medicinsk teknik för personlig hälsa avser vi monitorering av patienter med risk för att utveckla en viss sjukdom eller som har en kronisk sjukdom. Bland delprojekt som vi arbetar med kan nämnas: Tekniska metoder för att patienter kan bo kvar i sin hemmiljö, Informationsteknik för att underlätta patientens vardagsbestyr, Mät- och kommunikationsplattformar för fysiologiska signaler/labprover, Trådlös informationsöverföring, Journalsystem för distribuerad vård samt Monitorering/övervakning av fysiologiska parameter kopplade till kroniska sjudomar

    Medicinsk teknik för bildbaserad diagnostik och terapi blir allt viktigare i en högteknologisk sjukvård. Vi arbetar med att vidareutveckla tekniken framför allt genom att på nya sätt processa bildinformationen. Exempel på delprojket som vi driver är: Avbildning av vävnad med hjälp av mikrovågstomografi, Utveckling av ny MR-teknik för hjärtundersökning, Avancerad bildbehandling av datortomografibilder och mikroskopbilder och Medicinska bilder för att simulera och styra behandling.

    Projektet har pågått i ca 2 år och bland hittills uppnådda resultat kan nämnas ca 60 identifierade produktidéer, att 20 produktidéer har tagits till klinisk evaluering, att 9 prototyper har kommit till en kommersialiseringsfas och att 3 nya företag hittills har bildats genom NovaMedTechs medverkan.

  • 45.
    Hult, Peter
    et al.
    Linköping University, Department of Biomedical Engineering.
    Alod, Tanja
    Linköping University, Department of Biomedical Engineering.
    Rattfält, Linda
    Linköping University, Department of Biomedical Engineering.
    Textile electrodes - An alternative as ECG electrodes in home health care?2006Conference paper (Other academic)
    Abstract [en]

    The use of electrocardiogram (ECG) is a well known and widely used method. However, when the home health care is expanding, new demands for ECG equipment is seen. It would be desirable if electrodes would be more comfortable to use, especially for long-time registrations. The contact between electrodes and skin becomes worse with time and electrodes can also irritate the skin. With textile technology of today, yarns can be created with leading materials [1]. Thin threads of metal are spun into yarn and can be used for weaving or knitting fabrics. These fabrics can be used as electrodes for ECG registration, with the advantage of textile properties. By integrating such electrodes in clothes, the electrodes could become more wearable and more suitable for some ECG registrations [2, 3, 4] . The difficulty of distinguishing QRS-complexes will be used for studying signals from textile electrodes. In this study, three different textile sensors was compared in order to investigate influences in the ECG signal caused by material, size or structure. Such influences could contaminate the signal with different types of noise and make it difficult to distinguish the characteristics of the ECG [5].

  • 46.
    Hult, Peter
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Lindén, Maria
    Institutionen för datavetenskap och elektronik, Mälardalens högskola, Västerås, Sverige.
    Rattfält, Linda
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Distribuerad vård - Möjligheter, Behov och svårigheter.2006Conference paper (Other academic)
  • 47.
    Hultman, Martin
    et al.
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Fredriksson, Ingemar
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering. Perimed AB, Järfälla-Stockholm, Sweden.
    Larsson, Marcus
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Alvandpour, Atila
    Linköping University, Department of Electrical Engineering, Integrated Circuits and Systems. Linköping University, Faculty of Science & Engineering.
    Strömberg, Tomas
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    A 15.6 frames per second 1 megapixel Multiple Exposure Laser Speckle Contrast Imaging setup2018In: Journal of Biophotonics, ISSN 1864-063X, E-ISSN 1864-0648, Vol. 11, no 2, article id e201700069Article in journal (Refereed)
    Abstract [en]

    A multiple exposure laser speckle contrast imaging (MELSCI) setup for visualizing blood perfusion was developed using a field programmable gate array (FPGA), connected to a 1000 frames per second (fps) 1-megapixel camera sensor. Multiple exposure time images at 1, 2, 4, 8, 16, 32 and 64 milliseconds were calculated by cumulative summation of 64 consecutive snapshot images. The local contrast was calculated for all exposure times using regions of 4 × 4 pixels. Averaging of multiple contrast images from the 64-millisecond acquisition was done to improve the signal-to-noise ratio. The results show that with an effective implementation of the algorithm on an FPGA, contrast images at all exposure times can be calculated in only 28 milliseconds. The algorithm was applied to data recorded during a 5 minutes finger occlusion. Expected contrast changes were found during occlusion and the following hyperemia in the occluded finger, while unprovoked fingers showed constant contrast during the experiment. The developed setup is capable of massive data processing on an FPGA that enables processing of MELSCI data in 15.6 fps (1000/64 milliseconds). It also leads to improved frame rates, enhanced image quality and enables the calculation of improved microcirculatory perfusion estimates compared to single exposure time systems.

  • 48.
    Högberg Mårder, Thérèse
    Linköping University, Department of Biomedical Engineering.
    Modelling breast cancer pathology reports using SNOMED CT and openEHR2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With a longer-living population and an increase in cancer incidence the health care’s workload has increased over the past decade. The treatment process of a cancer patient is dependant on clinical information collected and communicated from the pathology department. With a standardised and structured pathology report the information communicated can become easier to interpret and will fa- cilitate the search for important parameters.

    This master thesis aims to develop a template prototype to replace four static free-text templates used in the area of breast cancer pathology at the pathology department at Region Östergötland. The end product was intends to store docu- mented information in a structured manner through structured data, in order to obtain semantic interoperability.

    Semantic interoperability means that different systems are able to communicate with each other in such a way that the information is handled and interpreted equally by the systems. By using certain standards such as openEHR archetypes and SNOMED CT concepts, the data becomes uniform and unambiguous. When that is achieved, information can be sent more easily between systems such as patient health data if an individual moves between different cities where the hos- pitals have different medical records systems.

    The result of the master thesis is a single template that incorporates all the parts from the four static templates currently used at Region Östergötland. To avoid a large and cumbersome template for the end-user the template is built with con- ditions that changed the appearance of the template while it is being filled in, making it dynamic.

  • 49.
    Jager, Edwin
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Book Review: Microfluidics in Detection Science – Lab-on-a-Chip Technologies, H.O. Fatoyinbo, F.H. Labeed (Eds.). Royal Society of Chemistry, Cambridge (2015). 281 pp., £145 GBP, ISBN 978-84973-638-12015In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 71, p. 483-484Article in journal (Refereed)
  • 50.
    Johansson, Johannes
    et al.
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Alonso, Fabiola
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Modelling Details for Electric Field Simulations of Deep Brain Stimulation2019In: WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING 2018, VOL 1, SPRINGER , 2019, Vol. 68, no 1, p. 645-648Conference paper (Refereed)
    Abstract [en]

    Deep brain stimulation is a well-established technique for symptomatic treatment of e.g. Parkinsons disease and essential tremor. Computer simulations using the finite element method (FEM) are widely used to estimate the affected area around the DBS electrodes. For the reliability of the simulations, it is important to match used simulation parameters with experimental data. One such parameter is the electric field magnitude threshold EFt required for axon stimulation. Another is the conductivity of the perielectrode space (PES) around the electrode. At the acute stage after surgery the PES will be characterized by an increased conductivity due to inflammation and edema while the later chronic stage will be characterized by a lower conductivity due to gliosis and minor scar formation. In this study, the EFt and the electric conductivity of the PES have been estimated by comparing FEM simulations with clinical studies of activation distance, pulse length and electrode impedance. The resulting estimates are an EFt of 0.2 V/mm at the common pulse width of 60 mu s and a chronaxie of 62 mu s. Estimated electric conductivities for the PES are 0.14 S/m in the acute stage and 0.05 S/m in the chronic stage, assuming a PES width of 250 mu m. These values are thus experimentally justified to use in FEM simulations of DBS.

123 1 - 50 of 135
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf