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  • 101.
    Antonsson, Johan
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Optical measurements in brain tissue during radio frequency lesioning2004Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Radio frequency (RF) lesioning is a well well-known procedure within the field of stereotactic neurosurgery, commonly used for the treatment of movement disorders. During the intervention, an RF-electrode is inserted into the deeper parts of the brain, where a small volume of malfunctioning brain tissue will be coagulated. This procedure is irreversible, as a result, the size and position of the created lesion is crucial in order to avoid unwanted side effects. In this thesis a further development of the RF-technology is presented in order to follow a lesioning process and to estimate the created lesion size. Software, electronics, fiber optics and an RF-electrode equipped with optical fibers was developed and evaluated.

    Diffuse reflectance spectroscopy measurements at 450-800 nm in the central gray of porcine brain have been performed with the developed RF-electrode. Measurements of white and gray brain matter showed a large reflectance difference in the investigated wavelength interval, with higher reflectivity for white brain matter. Reflectance differences between native and coagulated, white and gray brain matter were also found .

    In-vitro laser Doppler perfusion monitoring measurements at 633 nm have also been performed in a newly designed flow model. An albumin solution with added glass microspheres was placed on top of a revolving disc. The motion of the liquid surrounding the electrode tip simulated a perfusion situation. Changes in both laser Doppler perfusion and total backscattered light intensity signals were collected during the creation of different sized coagulations. The volume, width and length of the created coagulations are correlated to the measured signal changes in-vitro, where larger coagulations displayed larger signal changes. The laser Doppler perfusion and backscattered light intensity signals can be used to follow the lesioning time course and estimate the developed lesion size in-vitro.

    Delarbeid
    1. In-vivo reflection spectroscopy measurements in pig brain during stereotactic surgery
    Åpne denne publikasjonen i ny fane eller vindu >>In-vivo reflection spectroscopy measurements in pig brain during stereotactic surgery
    2003 (engelsk)Inngår i: Biophotonics West: Biomedical Optics, 2003, Vol. 4958, s. 242-250Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Radiofrequency (RF) lesioning in the human brain is a commonsurgical therapy for relieving severe pain as well as formovement disorders such as Parkinsonia. During the procedure a smallelectrode is introduced by stereotactic means towards a target arealocalized by CT or MRI. An RF-current is applied throughthe electrode tip when positioned in the target area. Thetissue in the proximity of the tip is heated bythe current and finally coagulated.The overall aim of this studywas to improve the RF-technique and its ability to estimatelesion size by means of optical methods. Therefore, the opticaldifferences between white and gray matter, as well as lesionedand unlesioned tissue were investigated. Reflection spectroscopy measurements in therange of 450-800 nm were conducted on fully anesthetized pigsduring stereotactic RF-lesioning (n=6). Light from a tungsten lamp wasguided to the electrode tip through optical fibers, inserted alonga 2 mm in diameter monopolar RF-electrode. Measurements were performedin steps of 0-10 mm from the target in eachhemisphere towards the entry point of the skull. In thecentral gray of the porcine brain measurements were performed bothbefore and after the creation of a lesion. A totalof 55 spectra were collected during this study. Correlation totissue type was done using post-operative MR-images. The spectral signaturefor white and gray matter differs significantly for the entirespectral range of 450-800 nm. Pre- and post-lesioning reflection spectroscopyshowed the largest differences below 600 and above 620 nm,which implies that lasers within this wavelength range may beuseful for in-vivo measurements of tissue optical changes during RF-lesioning.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-14234 (URN)10.1117/12.476131 (DOI)
    Tilgjengelig fra: 2007-01-26 Laget: 2007-01-26 Sist oppdatert: 2017-02-22bibliografisk kontrollert
    2. Radio frequency electrode system for optical lesion size estimation in functional neurosurgery
    Åpne denne publikasjonen i ny fane eller vindu >>Radio frequency electrode system for optical lesion size estimation in functional neurosurgery
    2005 (engelsk)Inngår i: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 10, nr 3, s. 1-6Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Radiofrequency(RF) lesioning in the human brain is one possible surgicaltherapy for severe pain as well as movement disorders. Oneobstacle for a safer lesioning procedure is the lack ofsize monitoring. The aim of this study was to investigateif changes in laser Doppler or intensity signals could beused as markers for size estimation during experimental RF lesioning.A 2 mm in diameter monopolar RF electrode was equippedwith optical fibers and connected to a digital laser Dopplersystem. The optical RF electrode's performance was equal to astandard RF electrode with the same dimensions. An albumin solutionwith scatterers was used to evaluate the intensity and laserDoppler signal changes during lesioning at 70, 80, and 90 °C.Significant signal changes were found for these three different clotsizes, represented by the temperatures (p<0.05,  n=10). The volume, width, andlength of the created coagulations were correlated to the intensitysignal changes (r=0.88, n=30, p<0.0001) and to the perfusion signalchanges (r=0.81, n=30, p<0.0001). Both static and Doppler-shifted light canbe used to follow the lesioning procedure as well asbeing used for lesion size estimation during experimental RF lesioning.

    sted, utgiver, år, opplag, sider
    SPIE - International Society for Optical Engineering, 2005
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-14232 (URN)10.1117/1.1924615 (DOI)000235127400040 ()16229664 (PubMedID)2-s2.0-24144476322 (Scopus ID)
    Tilgjengelig fra: 2007-01-26 Laget: 2007-01-26 Sist oppdatert: 2017-12-13bibliografisk kontrollert
  • 102.
    Antonsson, Johan
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Babic, Ankica
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik.
    Ahn, Henrik Casimir
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Thoraxkirurgi. Östergötlands Läns Landsting, Hjärtcentrum, Thorax-kärlkliniken.
    Quality of life using profile in coronary artery bypass surgery patients1999Inngår i: AMIA99,1999, Philadelphia: Hanley & Belfus Inc , 1999, s. 1013-Konferansepaper (Fagfellevurdert)
  • 103.
    Antonsson, Johan
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Eriksson, Ola
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Blomstedt, Patric
    Department of Neurosurgery, University Hospital, Umeå, Sweden.
    Bergenheim, Tommy
    Department of Neurosurgery, University Hospital, Umeå, Sweden.
    Hariz, Marwan
    Department of Neurosurgery, University Hospital, Umeå, Sweden.
    Richter, Johan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Zsigmond, Peter
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Neurokirurgi. Linköpings universitet, Hälsouniversitetet.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Diffuse reflectance spectroscopy measurements for tissue type discrimination during deep brain stimulation2008Inngår i: Journal of neural engineering, ISSN 1741-2560, Vol. 5, nr 2, s. 185-190Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Diffuse reflectance spectroscopy as a method for improving intracerebral guidance during functional neurosurgery has been investigated. An optical probe was developed for measurements during stereotactic and functional neurosurgery in man. The aim of the study was to investigate the spectral differences between white and grey matter and between white matter and functional targets. Diffuse reflectance spectroscopy measurements in ten patients were recorded at incremental steps towards and in three different functional targets (STN, GPi and Zi). The recorded spectra along the trajectory were sorted into white or grey matter, based on preoperative MRI images or the recorded spectral shape and intensity. The difference between tissue types was calculated as a quotient. Significant intensity differences between white and grey matter were found to be at least 14% (p < 0.05) and 20% (p < 0.0001) for MRI and spectral-sorted data respectively. The reflectance difference between white matter and the functional targets of GPi was higher than for STN and Zi. The results indicate that diffuse reflectance spectroscopy has a potential to be developed to a suitable complement to other intracerebral guidance methods.

  • 104.
    Antonsson, Johan
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Eriksson, Ola
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Lundberg, Peter
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Optical measurements during experimental stereotactic radiofrequency lesioning2006Inngår i: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 84, nr 2-3, s. 118-124Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this study was to evaluate in vivo a laser Doppler measurement system in porcine brain tissue during thermal lesioning. A 2-mm monopolar radiofrequency lesioning electrode was equipped with optical fibers in order to monitor the lesioning procedure. Laser Doppler and backscattered light intensity signals were measured along the electrode trajectory and during bilateral lesioning in the central gray (70, 80 and 90°C, n = 14). The time course of the coagulation process could be followed by optical recordings. Two separate groups of tissue were identified from the intensity signals. The changes in the perfusion levels in both groups displayed significant changes (p < 0.05, n = 48) at all temperature settings, while backscattered light intensity was significant for only one group at the different temperatures (p < 0.05, n = 39). These results indicate that optical measurements correlate with lesion development in vivo. The study also indicates that it is possible to follow the lesioning process intra-operatively.

  • 105.
    Antonsson, Johan
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Eriksson, Ola
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    In-vivo reflection spectroscopy measurements in pig brain during stereotactic surgery2003Inngår i: Biophotonics West: Biomedical Optics, 2003, Vol. 4958, s. 242-250Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Radiofrequency (RF) lesioning in the human brain is a commonsurgical therapy for relieving severe pain as well as formovement disorders such as Parkinsonia. During the procedure a smallelectrode is introduced by stereotactic means towards a target arealocalized by CT or MRI. An RF-current is applied throughthe electrode tip when positioned in the target area. Thetissue in the proximity of the tip is heated bythe current and finally coagulated.The overall aim of this studywas to improve the RF-technique and its ability to estimatelesion size by means of optical methods. Therefore, the opticaldifferences between white and gray matter, as well as lesionedand unlesioned tissue were investigated. Reflection spectroscopy measurements in therange of 450-800 nm were conducted on fully anesthetized pigsduring stereotactic RF-lesioning (n=6). Light from a tungsten lamp wasguided to the electrode tip through optical fibers, inserted alonga 2 mm in diameter monopolar RF-electrode. Measurements were performedin steps of 0-10 mm from the target in eachhemisphere towards the entry point of the skull. In thecentral gray of the porcine brain measurements were performed bothbefore and after the creation of a lesion. A totalof 55 spectra were collected during this study. Correlation totissue type was done using post-operative MR-images. The spectral signaturefor white and gray matter differs significantly for the entirespectral range of 450-800 nm. Pre- and post-lesioning reflection spectroscopyshowed the largest differences below 600 and above 620 nm,which implies that lasers within this wavelength range may beuseful for in-vivo measurements of tissue optical changes during RF-lesioning.

  • 106.
    Antonsson, Johan
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Eriksson, Ola
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Radio frequency electrode system for optical lesion size estimation in functional neurosurgery2005Inngår i: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 10, nr 3, s. 1-6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Radiofrequency(RF) lesioning in the human brain is one possible surgicaltherapy for severe pain as well as movement disorders. Oneobstacle for a safer lesioning procedure is the lack ofsize monitoring. The aim of this study was to investigateif changes in laser Doppler or intensity signals could beused as markers for size estimation during experimental RF lesioning.A 2 mm in diameter monopolar RF electrode was equippedwith optical fibers and connected to a digital laser Dopplersystem. The optical RF electrode's performance was equal to astandard RF electrode with the same dimensions. An albumin solutionwith scatterers was used to evaluate the intensity and laserDoppler signal changes during lesioning at 70, 80, and 90 °C.Significant signal changes were found for these three different clotsizes, represented by the temperatures (p<0.05,  n=10). The volume, width, andlength of the created coagulations were correlated to the intensitysignal changes (r=0.88, n=30, p<0.0001) and to the perfusion signalchanges (r=0.81, n=30, p<0.0001). Both static and Doppler-shifted light canbe used to follow the lesioning procedure as well asbeing used for lesion size estimation during experimental RF lesioning.

  • 107.
    Antonsson, Johan
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Granfeldt, Hans
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Thoraxkirurgi. Östergötlands Läns Landsting, Hjärtcentrum, Thorax-kärlkliniken.
    Kircher, Albert
    Technical University Graz Austria.
    Babic, Ankica
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik.
    Lönn, Urban
    Uppsala .
    Ahn, Henrik Casimir
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Thoraxkirurgi. Östergötlands Läns Landsting, Hjärtcentrum, Thorax-kärlkliniken.
    Design of a clinical decision support system for assist support devices in thoracic surgery2000Inngår i: AMIA,2000, Philadelphia: Hanley & Belfus Inc, , 2000Konferansepaper (Fagfellevurdert)
  • 108.
    Arganda-Carreras, Ignacio
    et al.
    Institute Jean Pierre Bourgin, France.
    Turaga, Srinivas C.
    Howard Hughes Medical Institute, VA USA.
    Berger, Daniel P.
    Harvard University, MA 02138 USA.
    Ciresan, Dan
    Scuola University of Profess Svizzera Italiana, Switzerland.
    Giusti, Alessandro
    Scuola University of Profess Svizzera Italiana, Switzerland.
    Gambardella, Luca M.
    Scuola University of Profess Svizzera Italiana, Switzerland.
    Schmidhuber, Juergen
    Scuola University of Profess Svizzera Italiana, Switzerland.
    Laptev, Dmitry
    ETH, Switzerland.
    Dwivedi, Sarvesh
    ETH, Switzerland.
    Buhmann, Joachim M.
    ETH, Switzerland.
    Liu, Ting
    University of Utah, UT USA.
    Seyedhosseini, Mojtaba
    University of Utah, UT USA.
    Tasdizen, Tolga
    University of Utah, UT USA.
    Kamentsky, Lee
    Broad Institute, MA USA.
    Burget, Radim
    Brno University of Technology, Czech Republic.
    Uher, Vaclav
    Brno University of Technology, Czech Republic.
    Tan, Xiao
    University of New S Wales, Australia.
    Sun, Changming
    CSIRO, Australia.
    Pham, Tuan
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Bas, Erhan
    Howard Hughes Medical Institute, VA USA.
    Uzunbas, Mustafa G.
    Rutgers State University, NJ 08903 USA.
    Cardona, Albert
    Howard Hughes Medical Institute, VA USA.
    Schindelin, Johannes
    University of Wisconsin, WI USA.
    Sebastian Seung, H.
    Princeton University, NJ 08544 USA; Princeton University, NJ 08544 USA.
    Crowdsourcing the creation of image segmentation algorithms for connectomics2015Inngår i: Frontiers in Neuroanatomy, ISSN 1662-5129, E-ISSN 1662-5129, Vol. 9, nr 142Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To stimulate progress in automating the reconstruction of neural circuits, we organized the first international challenge on 2D segmentation of electron microscopic (EM) images of the brain. Participants submitted boundary maps predicted for a test set of images, and were scored based on their agreement with a consensus of human expert annotations. The winning team had no prior experience with EM images, and employed a convolutional network. This "deep learning" approach has since become accepted as a standard for segmentation of FM images. The challenge has continued to accept submissions, and the best so far has resulted from cooperation between two teams. The challenge has probably saturated, as algorithms cannot progress beyond limits set by ambiguities inherent in 2D scoring and the size of the test dataset. Retrospective evaluation of the challenge scoring system reveals that it was not sufficiently robust to variations in the widths of neurite borders. We propose a solution to this problem, which should be useful for a future 3D segmentation challenge.

  • 109.
    Arildsson, Mikael
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Origin and processing of laser Doppler spectra2000Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Laser Doppler Flowmetry (LDF) is a technique for studying microvascular blood flow. Laser light is guided to the tissue and the backscattered light, after being Doppler shifted by moving Red Blood Cells (RBCs), is detected using a heterodyne process. In Laser Doppler Perfusion Monitoring, the light is guided to and from the tissue using optical fibers, whilst in Laser Doppler Perfusion Imaging (LDPI), a freely impinging laser beam is used. The Power Spectral Density (PSD) of the photodetector current constitutes the LDF spectrum and can be processed to yield an estimate of the tissue perfusion.

    The aim of this thesis was to study the origin and suggest adequate processing of the LDF spectra from both a technical and a physiological perspective.

    The orientation and length of the average scattering vector resulting from a RBC/photon interaction, are altered when changing the laser source wavelength. It has been shown theoretically that the change in the orientation and length do not alter the average frequency shift of the scattering event. In vivo measurements on a low and a high perfused area using the wavelengths 632.8 nm and 780 nm respectively, confirm the theoretical findings. The heterodyne efficiency of the detector increases for longer wavelengths, giving higher photodetector signal amplitude.

    A method for differentiating high velocity flows, by changing the filtering of the LDF spectra is presented. Emphasis is given to higher frequencies, including information from higher flow velocities.

    The scanning mode and the shape of the laser beam. influence the spectral signature in LDPI. In order to maintain a high signal quality, a stepwise mode is to be preferred. The continuous mode induces large spectral components that depend on the scanning speed and the tissue surface roughness. Using a slightly divergent beam minimizes the inlluence of the distance between the detector and the tissue surface.

    The physiological perspective includes two randomized and placebo controlled studies of the rela tionship between topical skin analgesia and the perfusion response to different local stimuli. In the first study, it was shown that analgesia using EMLA® cream during local heating, changes the dynamic flow regulation to a persistent and delayed perfusion increase. This was not observed in untreated or placebo treated skin. In the second study, this heating response was positively related to longer treatment times and. hence. to higher intradermal concentrations of the analgesics. By using capillary microscopy. it was shown that analgesic cream treatment for at least one hour reduces the number of physiologically active capillaries by 50%, while LDf perfusion remains unaltered. After local heating, the LDF perfusion increased, in 9/11 subjects by an average of 8.7 times, while the number of capillaries remained decreased. These findings suggest a low capillary influence of the LDF signal in human skin.

    Delarbeid
    1. Critical design parameters in laser Doppler perfusion imaging
    Åpne denne publikasjonen i ny fane eller vindu >>Critical design parameters in laser Doppler perfusion imaging
    1996 (engelsk)Inngår i: Proc. SPIE 2678: Optical Diagnostics of Living Cells and Biofluids / [ed] Daniel L. Farkas; Robert C. Leif; Alexander V. Priezzhev; Toshimitsu Asakura; Bruce J. Tromberg, SPIE Proceedings Series , 1996, Vol. 2678, s. 401-408Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Laser Doppler Perfusion Imaging (LDPI) is a method for visualization of tissue blood perfusion. A low power laser beam is used to step-wise scan a tissue area of interest and a perfusion estimate based on the backscattered, partially Doppler broadened, light is generated. Although the basic operating principle of LDPI is the same as that of conventional Laser Doppler Perfusion Monitoring (LDPM), significant differences exist between the implementation of the methods which must be taken into account in order to generate high quality perfusion images. The purpose of this study is to investigate the relevance of a number of LDPI design parameters, such as:

    (1) The influence of artifact noise when using a continuously moving laser beam instead of a step-wise moving beam to scan the image.

    (2) The signal processor output's dependency on the distance between the measurement object and the scanner head when using collimated laser light.

    (3) The speed and mode of the scanning.

    The results show a substantial rise in the noise level when using a continuously moving beam as opposed to a step-wise. Skin measurements using a collimated laser beam demonstrated an amplification factor dependency on the distance between the skin surface and the scanner head not present when using a divergent laser beam. The scanning speed is limited by the trade-off between the Doppler signal lower cut-off frequency and the image quality.

    sted, utgiver, år, opplag, sider
    SPIE Proceedings Series, 1996
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-33211 (URN)10.1117/12.239527 (DOI)19198 (Lokal ID)9780819420527 (ISBN)19198 (Arkivnummer)19198 (OAI)
    Konferanse
    Optical Diagnostics of Living Cells and Biofluids, San Jose, CA | January 27, 1996
    Tilgjengelig fra: 2009-10-09 Laget: 2009-10-09 Sist oppdatert: 2016-05-04
    2. Higher order moment processing of laser Doppler perfusion signals
    Åpne denne publikasjonen i ny fane eller vindu >>Higher order moment processing of laser Doppler perfusion signals
    1997 (engelsk)Inngår i: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 2, nr 4, s. 358-363Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The laser Doppler technique is used to assess tissue perfusion. Traditionally an integrated, ω-weighted (first-order filter) power spectrum is used to estimate perfusion. In order to be able to obtain selective information about the flow in vessels with different blood cell velocities, higher order filters have been implemented, investigated, and evaluated. Theoretical considerations show that the output of the signal processor will depend on the flow speed, for a given concentration of blood cells, according to Soutνn where v is the average blood cell speed and n is the spectral filter order. An implementation of filters using zero-, first-, second-, and third-order spectral moments was utilized to experimentally verify the theory by using a laser Doppler perfusion imager. Two different flow models were utilized: A Plexiglas model was used to demonstrate the various signatures of the power spectrum for different flow speeds and filter orders, whereas a Delrin model was used to study the relationship between the flow velocity and the output of the signal processor for the different filters. The results show good agreement with theory and also good reproducibility. Recordings made on the skin of the wrist area demonstrated that the flow in small veins can be visualized by the use of higher spectral orders.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-33080 (URN)10.1117/12.281499 (DOI)19050 (Lokal ID)19050 (Arkivnummer)19050 (OAI)
    Tilgjengelig fra: 2009-10-09 Laget: 2009-10-09 Sist oppdatert: 2017-12-13
    3. Spectral signature and heterodyne efficiency for different wavelengths in laser Doppler flowmetry
    Åpne denne publikasjonen i ny fane eller vindu >>Spectral signature and heterodyne efficiency for different wavelengths in laser Doppler flowmetry
    2002 (engelsk)Inngår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 40, nr 1, s. 85-89Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Laser Doppler perfusion monitoring and imaging technologies generate time traces and two-dimensional flow maps of the microcirculation. With the goal of reaching different tissue depths, these technologies are equipped with lassers operating at different wavelengths λ. The fact that the average scattering angle, at a single scattering event, between a photon and a red blood cell increases with λ is compensated for by a 1/λ effect in the scattering vector, rendering the average frequency shift virtually independent of the choice of wavelength. Monte Carlo simulations showed that the corresponding spectral signature of the Doppler signals for λ=632.8nm and 780nm were close to identical. The theoretical predictions were verified by calculating the centre-of-gravity (COG) frequency of the laser Doppler power spectral density for the two wavelengths from forearm and finger skin, representing a low and high perfusion area, respectively (forearm COG=123 against 121Hz, finger COG=220 against 212 Hz). When the wavelength changes from 632.8nm to 780nm, the heterodyne efficiency of the detector and, thereby, the inherent system amplifcation increase. For tissues with identical microvascular flow conditions, the output signal therfore tends to increase in magnitude when shifting to longer wavelengths.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-24544 (URN)10.1007/BF02347700 (DOI)6703 (Lokal ID)6703 (Arkivnummer)6703 (OAI)
    Tilgjengelig fra: 2009-10-07 Laget: 2009-10-07 Sist oppdatert: 2017-12-13
    4. Effects on skin blood flow by provocation during local analgesia
    Åpne denne publikasjonen i ny fane eller vindu >>Effects on skin blood flow by provocation during local analgesia
    2000 (engelsk)Inngår i: Microvascular Research, ISSN 0026-2862, E-ISSN 1095-9319, Vol. 59, nr 1, s. 122-130Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Although topical analgesia cream has been used for several years, little is known about its effects on the microcirculation. Previous studies have shown a vasoconstrictive effect after short application times and a vasodilatation after longer application. It has also been shown that vasomotion does not occur in the analgesized skin. The present study was undertaken to investigate the alterations in skin blood perfusion following local cooling, local heating and pin-pricking after the establishment of analgesia. In 11 healthy volunteers, skin analgesia was attained by use of a eutectic mixture of lidocaine and prilocaine (EMLA, Astra Pain Control AB, Sweden) applied to the skin three hours prior to provocation. The changes in skin blood perfusion, after applying three different provocation methods, were studied using the laser Doppler technique. Local cooling and heating to temperatures of +10 and +45°C, respectively, were applied for 9 s by use of a copper probe (Ø12 mm). In the pin-prick provocation method, a combined effect of deflection and penetration of the skin to in total 3 mm was attained. Identical provocation methods were applied to placebo treated and untreated skin areas. After heat provocation, significant differences in the perfusion response between the treatments were seen (P < 0.0001). Skin areas treated with analgesia cream responded with a slow increase in perfusion that persisted beyond the four minute measurement period. Placebo and untreated areas decreased their perfusion over time. After cooling a significant reduction in skin perfusion was seen, irrespective of the treatment. Similarly, after pin-pricking a perfusion increase was seen for all treatments. The findings indicate that topical analgesia influences the myogenic control of the blood flow in those vascular plexa measured by laser Doppler following heat provocation. No differences could be seen in the response to pin-pricking and cooling for the different treatments.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-30586 (URN)10.1006/mvre.1999.2205 (DOI)16177 (Lokal ID)16177 (Arkivnummer)16177 (OAI)
    Tilgjengelig fra: 2009-10-09 Laget: 2009-10-09 Sist oppdatert: 2017-12-13
    5. Skin capillary appearance and skin microvascular perfusion due to topical application of analgesia cream
    Åpne denne publikasjonen i ny fane eller vindu >>Skin capillary appearance and skin microvascular perfusion due to topical application of analgesia cream
    2000 (engelsk)Inngår i: Microvascular Research, ISSN 0026-2862, E-ISSN 1095-9319, Vol. 59, nr 1, s. 14-23Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Local topical analgesia changes basal skin perfusion and its regulation. In particular, the response induced by local heating, which in nontreated skin comprises a rapidly increased perfusion followed by a normalization within 30 s, is altered to a delayed and persistent perfusion increase. The response dependency to the analgesia cream application time, that is, the intradermal penetration of the analgesics and in which vascular plexa the response occurs, is not known. The aim of this study was to assess changes in the appearance of superficial skin capillaries and skin microvascular perfusion changes due to different application periods of topical analgesia cream (EMLA). Twelve subjects were treated with EMLA and placebo applied to the volar side of each forearm, respectively. The treatment areas were assigned different application times (20 min, 40 min, 1 h, 2 h, and 3 h). The areas were cleared from the creams and shortly thereafter provoked during 9 s with a probe heated to 45°C. To assess capillary number density and skin perfusion, capillary microscopy, and Laser Doppler perfusion imaging (LDPI), respectively, were used. The number density of physiologically active capillary was significantly decreased with longer application times of EMLA (P < 0.005). The LDPI-signal showed a persistent perfusion increase after provocation associated with increasing application time of the cream. This perfusion pattern was not seen after 20 min of treatment, but was present in 9 of 12 subjects after 3 h of treatment. No significant relationship between changes in the capillary number density and the LDF measurement was found. In conclusion, a longer application time and therefore a higher intradermal concentration and a deeper penetration of the analgesics was associated with a delayed and persistent perfusion increase after local heating. There was a discrepancy between changes in capillary number density and skin perfusion, indicating that the perfusion increase does not occur in the capillaries but in the deeper lying vessels. Hence, the contribution of the capillary perfusion to the LDF-signal is smaller than previously anticipated. Capillary number density and presumably their perfusion were decreased with longer application times.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-30587 (URN)10.1006/mvre.1999.2206 (DOI)16178 (Lokal ID)16178 (Arkivnummer)16178 (OAI)
    Tilgjengelig fra: 2009-10-09 Laget: 2009-10-09 Sist oppdatert: 2017-12-13
  • 110.
    Arildsson, Mikael
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Asker, Claes
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Salerud, Göran
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Strömberg, Tomas
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Skin capillary appearance and skin microvascular perfusion due to topical application of analgesia cream2000Inngår i: Microvascular Research, ISSN 0026-2862, E-ISSN 1095-9319, Vol. 59, nr 1, s. 14-23Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Local topical analgesia changes basal skin perfusion and its regulation. In particular, the response induced by local heating, which in nontreated skin comprises a rapidly increased perfusion followed by a normalization within 30 s, is altered to a delayed and persistent perfusion increase. The response dependency to the analgesia cream application time, that is, the intradermal penetration of the analgesics and in which vascular plexa the response occurs, is not known. The aim of this study was to assess changes in the appearance of superficial skin capillaries and skin microvascular perfusion changes due to different application periods of topical analgesia cream (EMLA). Twelve subjects were treated with EMLA and placebo applied to the volar side of each forearm, respectively. The treatment areas were assigned different application times (20 min, 40 min, 1 h, 2 h, and 3 h). The areas were cleared from the creams and shortly thereafter provoked during 9 s with a probe heated to 45°C. To assess capillary number density and skin perfusion, capillary microscopy, and Laser Doppler perfusion imaging (LDPI), respectively, were used. The number density of physiologically active capillary was significantly decreased with longer application times of EMLA (P < 0.005). The LDPI-signal showed a persistent perfusion increase after provocation associated with increasing application time of the cream. This perfusion pattern was not seen after 20 min of treatment, but was present in 9 of 12 subjects after 3 h of treatment. No significant relationship between changes in the capillary number density and the LDF measurement was found. In conclusion, a longer application time and therefore a higher intradermal concentration and a deeper penetration of the analgesics was associated with a delayed and persistent perfusion increase after local heating. There was a discrepancy between changes in capillary number density and skin perfusion, indicating that the perfusion increase does not occur in the capillaries but in the deeper lying vessels. Hence, the contribution of the capillary perfusion to the LDF-signal is smaller than previously anticipated. Capillary number density and presumably their perfusion were decreased with longer application times.

  • 111.
    Arildsson, Mikael
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Nilsson, Gert
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Strömberg, Tomas
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Effects on skin blood flow by provocation during local analgesia2000Inngår i: Microvascular Research, ISSN 0026-2862, E-ISSN 1095-9319, Vol. 59, nr 1, s. 122-130Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although topical analgesia cream has been used for several years, little is known about its effects on the microcirculation. Previous studies have shown a vasoconstrictive effect after short application times and a vasodilatation after longer application. It has also been shown that vasomotion does not occur in the analgesized skin. The present study was undertaken to investigate the alterations in skin blood perfusion following local cooling, local heating and pin-pricking after the establishment of analgesia. In 11 healthy volunteers, skin analgesia was attained by use of a eutectic mixture of lidocaine and prilocaine (EMLA, Astra Pain Control AB, Sweden) applied to the skin three hours prior to provocation. The changes in skin blood perfusion, after applying three different provocation methods, were studied using the laser Doppler technique. Local cooling and heating to temperatures of +10 and +45°C, respectively, were applied for 9 s by use of a copper probe (Ø12 mm). In the pin-prick provocation method, a combined effect of deflection and penetration of the skin to in total 3 mm was attained. Identical provocation methods were applied to placebo treated and untreated skin areas. After heat provocation, significant differences in the perfusion response between the treatments were seen (P < 0.0001). Skin areas treated with analgesia cream responded with a slow increase in perfusion that persisted beyond the four minute measurement period. Placebo and untreated areas decreased their perfusion over time. After cooling a significant reduction in skin perfusion was seen, irrespective of the treatment. Similarly, after pin-pricking a perfusion increase was seen for all treatments. The findings indicate that topical analgesia influences the myogenic control of the blood flow in those vascular plexa measured by laser Doppler following heat provocation. No differences could be seen in the response to pin-pricking and cooling for the different treatments.

  • 112.
    Arildsson, Mikael
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Nilsson, Gert
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Strömberg, Tomas
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Spectral signature and heterodyne efficiency for different wavelengths in laser Doppler flowmetry2002Inngår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 40, nr 1, s. 85-89Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Laser Doppler perfusion monitoring and imaging technologies generate time traces and two-dimensional flow maps of the microcirculation. With the goal of reaching different tissue depths, these technologies are equipped with lassers operating at different wavelengths λ. The fact that the average scattering angle, at a single scattering event, between a photon and a red blood cell increases with λ is compensated for by a 1/λ effect in the scattering vector, rendering the average frequency shift virtually independent of the choice of wavelength. Monte Carlo simulations showed that the corresponding spectral signature of the Doppler signals for λ=632.8nm and 780nm were close to identical. The theoretical predictions were verified by calculating the centre-of-gravity (COG) frequency of the laser Doppler power spectral density for the two wavelengths from forearm and finger skin, representing a low and high perfusion area, respectively (forearm COG=123 against 121Hz, finger COG=220 against 212 Hz). When the wavelength changes from 632.8nm to 780nm, the heterodyne efficiency of the detector and, thereby, the inherent system amplifcation increase. For tissues with identical microvascular flow conditions, the output signal therfore tends to increase in magnitude when shifting to longer wavelengths.

  • 113.
    Arildsson, Mikael
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Nilsson, Gert
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Critical design parameters in laser Doppler perfusion imaging1996Inngår i: Proc. SPIE 2678: Optical Diagnostics of Living Cells and Biofluids / [ed] Daniel L. Farkas; Robert C. Leif; Alexander V. Priezzhev; Toshimitsu Asakura; Bruce J. Tromberg, SPIE Proceedings Series , 1996, Vol. 2678, s. 401-408Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Laser Doppler Perfusion Imaging (LDPI) is a method for visualization of tissue blood perfusion. A low power laser beam is used to step-wise scan a tissue area of interest and a perfusion estimate based on the backscattered, partially Doppler broadened, light is generated. Although the basic operating principle of LDPI is the same as that of conventional Laser Doppler Perfusion Monitoring (LDPM), significant differences exist between the implementation of the methods which must be taken into account in order to generate high quality perfusion images. The purpose of this study is to investigate the relevance of a number of LDPI design parameters, such as:

    (1) The influence of artifact noise when using a continuously moving laser beam instead of a step-wise moving beam to scan the image.

    (2) The signal processor output's dependency on the distance between the measurement object and the scanner head when using collimated laser light.

    (3) The speed and mode of the scanning.

    The results show a substantial rise in the noise level when using a continuously moving beam as opposed to a step-wise. Skin measurements using a collimated laser beam demonstrated an amplification factor dependency on the distance between the skin surface and the scanner head not present when using a divergent laser beam. The scanning speed is limited by the trade-off between the Doppler signal lower cut-off frequency and the image quality.

  • 114.
    Arildsson, Mikael
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Nilsson, Gert
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Wårdell, Karin
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Tracking of small blood vessels by a new laser Doppler imaging technique1996Inngår i: SPIE-Bios96,1996, 1996Konferansepaper (Fagfellevurdert)
  • 115.
    Arildsson, Mikael
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Strömberg, Tomas
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Perfusion responses after local provocation of EMLA analgesized skin1999Inngår i: Congress of the International Society for Skin Imaging,1999, 1999Konferansepaper (Annet vitenskapelig)
  • 116.
    Arildsson, Mikael
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Nilsson, Gert
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Higher order moment processing of laser Doppler perfusion signals1997Inngår i: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 2, nr 4, s. 358-363Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The laser Doppler technique is used to assess tissue perfusion. Traditionally an integrated, ω-weighted (first-order filter) power spectrum is used to estimate perfusion. In order to be able to obtain selective information about the flow in vessels with different blood cell velocities, higher order filters have been implemented, investigated, and evaluated. Theoretical considerations show that the output of the signal processor will depend on the flow speed, for a given concentration of blood cells, according to Soutνn where v is the average blood cell speed and n is the spectral filter order. An implementation of filters using zero-, first-, second-, and third-order spectral moments was utilized to experimentally verify the theory by using a laser Doppler perfusion imager. Two different flow models were utilized: A Plexiglas model was used to demonstrate the various signatures of the power spectrum for different flow speeds and filter orders, whereas a Delrin model was used to study the relationship between the flow velocity and the output of the signal processor for the different filters. The results show good agreement with theory and also good reproducibility. Recordings made on the skin of the wrist area demonstrated that the flow in small veins can be visualized by the use of higher spectral orders.

  • 117.
    Arkad, Kristina
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Using Arden Syntax in decision support systems with special refrence to database integration1995Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Two of the most important issues in l!leveloping data-driven medical decision support systems are the choice of knowledge representation and the methods and technique for integration with the patient database. The main purpose of the Arden Syntax for Medical Logic Modules, which is the method of choice in this thesis, is to create a standard representation for data-driven decision support systems and to facilitate sharing of medical knowledge among different institutions and clinics. The main feature of the syntax is that it is easily readable and writeable, thereby allowing maintenance and transparency. The knowledge within a domain is braken down inta a number of independent medical logic modules (MLMs), where each module together with its logic also holds a description of its evocation criteria in terms of events and conditions related to patient data.

    This thesis addresses same of the problems with integration of a decision support system (OSS) inside a specific software engineering environment, together with issues in relation to database query handling. An architecture of a OSS based on Arden Syntax and its integration in an object-oriented environment is presented. The basic components of the OSS are the knowledge base composed of MLMs and the patient database with developed couplings between the knowledge base and the patient database. Since the MLM format is neutral to the local environment such as patient databases and computer platforms, these methods and tools are needed when realizing an efficient run-time OSS.

  • 118.
    Arkad, Kristina
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik.
    Gill, Hans
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik.
    Ludwigs, Ulf
    Södersjukhuset Stockholm.
    Shahsavar, Nosrat
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik.
    Xiao-Ming, Gao
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik.
    Wigertz, Ove
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik.
    Medical Logic Module (MLM) representation of knowledge in a ventilator treatment advisory system1991Inngår i: International Journal of Clinical Monitoring and Computing, ISSN 0167-9945, E-ISSN 2214-7314, Vol. 8, s. 43-48Artikkel i tidsskrift (Fagfellevurdert)
  • 119.
    Arkad, Kristina
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik.
    Xiao-Ming, Gao
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik.
    Shahsavar, Nosrat
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik.
    Wigertz, Ove
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik.
    Jean, Francois-Christophe
    Medical Informatics Dept Broussais University hospital, Paris.
    Degoulet, Patrice
    Medical Informatics Dept Broussais University Hospital, Paris.
    Integration of data driven decision support into the HELIOS environment1994Inngår i: International journal of bio-medical computing, ISSN 0020-7101, Vol. 34, s. 195-205Artikkel i tidsskrift (Fagfellevurdert)
  • 120.
    Arkad, Kristina
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik.
    Xiao-Ming, Gao
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik.
    Åhlfeldt, Hans
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik.
    Query-handling in MLM-based decision support systems1996Inngår i: Medical Informatics & the Internet in Medicine, Vol. 20, nr 3, s. 229-240Artikkel i tidsskrift (Fagfellevurdert)
  • 121.
    Aserod, Hanne
    et al.
    Univ Bergen, Norway.
    Babic, Ankica
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten. Univ Bergen, Norway.
    Designing a mobile system for safety reporting of arthroplasty adverse events2018Inngår i: EMBEC and NBC 2017, SPRINGER-VERLAG SINGAPORE PTE LTD , 2018, Vol. 65, s. 571-574Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a mobile software application development for safety reporting of adverse events within the field of arthroplasty. Proposed user interface enables entry of data specific for adverse events of the knee and hip implants. Besides the patient data, the system supports entry of the event, its classification (serious, non-serious), its follow up, as well as a connection to the database maintained within the Helse Bergen hospital information system. Safety reports can be initiated and retrieved on request and depending on the adjudication of the event; suspected severe events should be followed up until their resolution. Expert evaluation of the first design solution was performed using low fidelity prototype. It has shown that design was relevant, straightforward, done in a way that official reporting would commence. Some users were positive to the reporting, some felt it would demand more work. A comprehensive evaluation with different potential user groups is planned to meet their needs and understand their views.

  • 122.
    Aserod, Hanne
    et al.
    Univ Bergen, Norway.
    Babic, Ankica
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten. Univ Bergen, Norway.
    Pharmacovigilance Mobile Tool Design in the Field of Arhroplasty2017Inngår i: INFORMATICS EMPOWERS HEALTHCARE TRANSFORMATION, IOS PRESS , 2017, Vol. 238, s. 104-107Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Pharmacovigilance is an important part of the patient safety and it has a great appeal to physicians. It is concerned with the safety of medical devices and treatments in the light of understanding the risks and dangers based on the already reported safety issues. Internet resources such as the Manufacturer And User Facility Device Experience (MAUDE) web-site are often retrieved due to the lack of internal, local safety databases. The research looked at how Human Computer Interaction could improve user experience. We have designed data entry for safety reporting and pharmacovigilance based on the web-bases system called WebBISS (Web-based implant search system). The expectation is not only to improve usability, but also to stimulate physicians to enter their safety data and become also contributors, and not only users of information. The expert evaluation has been generally positive and encouraged stronger help and error reporting functions. The high fidelity design has given a good impression of the future mobile solution.

  • 123.
    Ask, P.
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Carlsson, P.Öberg, P.Å.Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.Pettersson, H.Tibbling, L.Törngren, P.
    An integrating transducer for oesophageal manometry.: The IV Nordic Meeting on Medical and Biological Engineering, Lyngby/Copenhagen, June 29 - July 2 1977.1977Konferanseproceedings (Annet vitenskapelig)
  • 124.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    EKG-elektroder: en svag länk vid övervakning1974Inngår i: Medicinsk Teknik, ISSN 0346-542X, nr 4, s. 12-15Artikkel i tidsskrift (Annet vitenskapelig)
  • 125.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    How to assess heart valve function with echocardiography1997Inngår i: European Conference on Engineering and Medicine,1997, 1997Konferansepaper (Fagfellevurdert)
  • 126.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Low-compliance perfusion pump for oesophageal manometry.1978Inngår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 16, nr 6, s. 732-738Artikkel i tidsskrift (Fagfellevurdert)
  • 127.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Measurement techniques for urodynamic investigations.1989Inngår i: Critical reviews in biomedical engineering, ISSN 0278-940X, E-ISSN 1943-619X, Vol. 17, nr 5, s. 413-449Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Important measurement techniques for investigating lower urinary tract function are flow and pressure measurements. The demands on urinary flowmeters and the measurement principles of balance type, rotating disc, dipstick, and air-displacement type are described. Urological pressure measurements are performed in the bladder, in the urethra, and in the abdominal cavity. Various fluid-filled and microtransducer systems are reviewed and demands for performance given. Differences in measuring a mechanical pressure, like in the urethra, and a fluid pressure in the bladder are discussed. Electromyography (EMG) technique is used to investigate various neurological disturbances in the lower urinary tract. The electrode technique is also described. Furthermore, techniques for incontinence detection are reviewed.

  • 128.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Oesophageal manometry: design and evaluation of measurement systems1978Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The aim of this study was to investigate the technical characteristics of oesophageal manometry systems and to improve the performance of these systems.

    The investigation of the characteristics of oesophageal manometry systems with non-perfused catheters or catheters perfused with a flow generated by a syringe pump did not show properties which fullfilled the requirements for accurate pressure measurements. The bandwidth of the pressure mesurement system was limited by the high compliance of the syringe perfusion pump. The characteristics of perfused systems were improved by the design of a low-compliance perfusion pump. The frequency characteristics of a pressure measurement system utilizing the low-compliance perfusion pump seemed to be determined by the properties of the cathetermanometer system. The frequency content of oesophageal peristaltic pressure was studied by use of a measurement system including the low-compliance perfusion pump. This investigation showed that a bandwidth of about 8 Hz or more is necessary for accurate measurements, which bandwidth can only be obtained with a low-compliance system. In a clinical study a non-perfused system and a system perfused with a syringe pump were compared simultaneously to a system with the low-compliance perfusion pump. The non-perfused system and the system perfused with the syringe pump gave lower peristaltic and sphincter pressure amplitudes than the system with the low-compliance perfusion pump. Since the oesophageal sphincter pressure varies in different radial directions, a pressure transducer has been devised, the mechanical design of which gives an integration of a radial pressure profile. The transducer has a linear static and dynamic transfer function.

  • 129.
    Ask, Per
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Brandberg, Joakim
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Janerot-Sjöberg, Birgitta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Karlsson, Matts
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk modellering och simulering.
    Loyd, Dan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanisk värmeteori och strömningslära.
    Wranne, Bengt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Assessment of heart valve function with echocardiography1997Inngår i: World Congress on Medical Physics and Biomedical Engineering,1997, 1997, s. 394-394Konferansepaper (Fagfellevurdert)
  • 130.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Carlsson, P
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Pettersson, H
    Törngren, P
    Tibbling, Lita
    Feedback system for control of abdominal compression in oesophageal investigations.1981Inngår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 19, nr 4, s. 501-503Artikkel i tidsskrift (Fagfellevurdert)
  • 131.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Edwall, G
    Johansson, K E
    Accuracy and choice of procedures in 24-hour oesophageal pH monitoring with monocrystalline antimony electrodes.1986Inngår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 24, nr 6, s. 602-608Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In 24 h pH monitoring, the evaluation is dependent on the absolute accuracy of the pH measurements. Several sources of error exist, such as the chemical composition of calibration buffers and reference electrode gel and the effect of temperature on both the pH and the reference electrodes. We investigated the magnitude of these errors for the monocrystalline antimony electrode. Similar analysis applies to other types of pH electrodes. The errors we found are important when choosing a calibration procedure. We recommend a calibration procedure in which the pH and reference electrodes are both put in a beaker with the calibration buffers prior to and after the 24 h measurements. The calibration buffers and the electrode gel should have a specially selected ion composition where, for example, the Cl-ion concentration is critical. Corrections for differences in temperature between the calibration and the in situ measurements must be added. The pH measurements can be checked by performing in situ calibration.

  • 132.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Edwall, G
    Johansson, K E
    Tibbling, Lita
    On the use of monocrystalline antimony pH electrodes in gastro-oesophageal functional disorders.1982Inngår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 20, nr 3, s. 383-389Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Monocrystalline antimony electrodes have been shown to be suitable for thein vivo determination of pH in blood, tissue and in the upper gastro-intestinal canal. Thanks to their small dimensions it has been possible to mount them into conventional manometry catheters for oesophageal investigation. The monocrystalline antimony pH electrode has several advantages over the conventional pH glass electrode; better accuracy, shorter rise time, smaller dimensions. The monocrystalline antimony electrode has been used for long-term registration of gastro-oesophageal reflux, for the oesophageal acid clearing test and for identification of the pH gradient zone between the gastric and oesophageal mucosa. Its use in combination with pressure sensors has added a new dimension to the diagnosis of functional disorders in the gastro-oesophageal region.

  • 133.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Edwall, G
    Tibbling, Lita
    Combined pH and pressure measurement device for oesophageal investigations.1981Inngår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 19, nr 4, s. 443-446Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A combined pH- and pressure-measurement device for oesophageal investigations has been designed using monocrystalline antimony pH electrodes and perfused polyvinyl catheters. The combined device facilitates pressure measurements simultaneously with pH recording, both distal and proximal to the pH electrode. The device is easier to pass through the nose to the oesophagus than the conventional glass pH electrode. pH and pressure measurements in the oesophagus are therefore simplified and valuable information about the function of the region of the lower oesophageal sphincter is added owing to the simultaneous recording of the two parameters.

  • 134.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    EDWALL, G
    Tibbling, Lita
    ESOPHAGEAL PH MEASUREMENTS USING AN ANTIMONY ELECTRODE1980Inngår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 18, nr 1Artikkel i tidsskrift (Fagfellevurdert)
  • 135.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Ekstrand, Kristina
    Katrineholm City, Sweden.
    Hult, Peter
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Lindén, Maria
    Mälardalen University, Västerås, Sweden.
    Pettersson, Nils-Erik
    Örebro County Council, Sweden.
    NovaMedTech - a regional program for supporting new medical technologies in personalized health care2012Inngår i: Studies in Health Technology and Informatics, ISSN 0926-9630, E-ISSN 1879-8365, Vol. 177, s. 71-5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    NovaMedTech is an initiative funded from EU structural funds for supporting new medical technologies for personalized health care. It aims at bringing these technologies into clinical use and to the health care market. The program has participants from health care, industry and academia in East middle Sweden. The first three year period of the program was successful in terms of product concepts tried clinically, and number of products brought to a commercialization phase. Further, the program has led to a large number of scientific publications. Among projects supported, we can mention: Intelligent sensor networks; A digital pen to collect medical information about health status from patients; A web-based intelligent stethoscope; Methodologies to measure local blood flow and nutrition using optical techniques; Blood flow assessment from ankle pressure measurements; Technologies for pressure ulcer prevention; An IR thermometer for improved accuracy; A technique that identifies individuals prone to commit suicide among depressed patients; Detection of infectious disease using an electronic nose; Identification of the lactate threshold from breath; Obesity measurements using special software and MR camera; and An optical probe guided tumor resection. During the present three years period emphasis will be on entrepreneurial activities supporting the commercialization and bringing products to the market.

  • 136.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Enberg, Anders
    Öberg, Åke
    Spånberg, Anders
    A SHORT-TIME-DELAY URINARY FLOWMETER1985Inngår i: Neurourology and Urodynamics, ISSN 0733-2467, E-ISSN 1520-6777, Vol. 4, nr 3, s. 247-256Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A urinary flowmeter has been designed, using a quickly rotating disc and a balance principle. The flowmeter has a fast and accurate response to changing flows. The time delay of the flowmeter is less than about 0.25 s. The improved accuracy in recording urinary flow using the presented flowmeter should make it possible to extract more information from the detrusor pressure and urinary flow relations, relevant for assessing lower urinary tract function.

  • 137.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    ENGVALL, J
    Loyd, Dan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    THEORETICAL AND EXPERIMENTAL-ANALYSIS OF AORTIC COARCTATION1989Inngår i: IMAGES OF THE TWENTY-FIRST CENTURY, PTS 1-6, 1989, Vol. 11, s. 103-103Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Aortic coarctation, which could severely influence the haemodynamic conditions of the body, is discussed. A theory has been developed which relates the pressure drop over the coarctation to the flow. This theory indicates that the pressure drop across the actual coarctation is related to the flow squared. For the collateral flow the expected pressure drop is either linearly or quadratically related to the flow. Model experiments and patient data support the present theoretical model

  • 138.
    Ask, Per
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Flaschemkampf, F
    Hasenkam, M
    Non-invasive approach to hemodynamic assessment of heart valves (INVADYNE)1997Inngår i: World congress on Medical Physics and Biomedical Engineering,1997, 1997, s. 1186-Konferansepaper (Fagfellevurdert)
  • 139.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Hult, Peter
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Filosofiska fakulteten.
    Fjallbrant, T
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Bioacoustic techniques is applicable to primary health care2001Inngår i: PROCEEDINGS OF THE 23RD ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-4: BUILDING NEW BRIDGES AT THE FRONTIERS OF ENGINEERING AND MEDICINE, 2001, Vol. 23, s. 1911-1914Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The stethoscope has been used diagnostically for nearly two hundred years to assess the heart function. We can envision the intelligent stethoscope which combines the advantages of the traditional instrument with advanced functionality for analysis of the signal and other information support. The bioacoustic technique is basically simple and robust and fits therefore into a scenario where investigations are performed in a distributed health care system as in primary health care or even home health care. We have focused on detection of respiratory sounds and third heart sounds. The later is performed with a new wavelet technique which makes it possible to automatically detect and identify the sounds and possibly relate them to myocardial insufficiency.

  • 140.
    Ask, Per
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Hägglund, Sture
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ASLAB - Application Systems Laboratory.
    Olsson, J.
    Pettersson, N-E
    Sjöqvist, Bengt Arne
    Åhlfeldt, Hans
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik.
    3G-satsning och 'pensionärsdatorer' kan lösa hälso- och sjukvårdens problem2003Inngår i: Läkartidningen, ISSN 0023-7205, E-ISSN 1652-7518, Vol. 100, s. 1257-1258Artikkel i tidsskrift (Annet vitenskapelig)
  • 141.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Hägglund, Sture
    Linköpings universitet, Institutionen för datavetenskap, Interaktiva och kognitiva system. Linköpings universitet, Tekniska högskolan.
    Olsson, Jan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling. Linköpings universitet, Filosofiska fakulteten.
    Pettersson, Nils-Erik
    Sjöqvist, Bengt-Arne
    Åhlfeldt, Hans
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    36-nätet och "pensionärsdatorer" kan bidra till att lösa sjukvårdens problem2003Inngår i: Läkartidningen, ISSN 0023-7205, E-ISSN 1652-7518, Vol. 100, nr 14, s. 1257-1258Artikkel i tidsskrift (Fagfellevurdert)
  • 142.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Hök, B
    Loyd, Dan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Teriö, H
    Bio-acoustic signals from stenotic tube flow: state of the art and perspectives for future methodological development.1995Inngår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 33, nr 5, s. 669-675Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To study the degree of stenosis from the acoustic signal generated by the turbulent flow in a stenotic vessel, so-called phonoangiography was first suggested over 20 years ago. A reason for the limited use of the technique today may be that, in the early work, the theory of how to relate the spectrum of the acoustic signal to the degree of the stenosis was not clear. However, during the last decade, the theoretical basis for this and other biological tube flow applications has been clarified. Now there is also easy access to computers for frequency analysis. A further explanation for the limited diagnostic use of bio-acoustic techniques for tube flow is the strong competition from ultrasound Doppler techniques. In the future, however, applications may be expected in biological tube flow where the non-invasive, simple and inexpensive bio-acoustic techniques will have a definite role as a diagnostic method.

  • 143.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Hök, Bertil
    PRESSURE MEASUREMENT TECHNIQUES IN URODYNAMIC INVESTIGATIONS1990Inngår i: Neurourology and Urodynamics, ISSN 0733-2467, E-ISSN 1520-6777, Vol. 9, nr 1, s. 1-15Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is apparent that the use of accurate pressure measurement techniques is essential for the outcome of urodynamic investigations. The aim of this paper is to estimate the demands on urodynamic pressure measurements and to review the properties of various techniques used. For the infused catheter technique, the dynamic properties are very much dependent on the complicance of the infusion system. With optimal infusion, the bandwidth and the pressure rise rate seem to be sufficient for most applications. Intraluminal microtransducers have a high bandwidth, but a certain fiber optic transducer cannot accurately measure mechanical pressure in the collapsed urethra. The principal differences in measuring hydrostatic pressure between the infused catheter technique and microtransducers should be observed. Flexion artefacts are a problem when measuring urethral pressure profiles. Newly developed transducers may offer a solution to this problem.

  • 144.
    Ask, Per
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Hök, Bertil
    Loyd, Dan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanisk värmeteori och strömningslära.
    Teriö, Heikki
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Bioacoustic signals from stenotic tube flow1995Inngår i: Medical & Biological Engineering & Computing, ISSN 0140-0118, Vol. 33, s. 669-675Artikkel i tidsskrift (Fagfellevurdert)
  • 145.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Levitan, H
    Robinson, P J
    Rapoport, S I
    Peripheral nerve as an osmometer: role of the perineurium in frog sciatic nerve.1983Inngår i: American Journal of Physiology, ISSN 0002-9513, E-ISSN 2163-5773, Vol. 244, nr 1, s. C75-81Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Measurements of volume and hydrostatic pressure in the frog sciatic nerve in vitro demonstrate that the nerve acts as an osmometer, in large part because the perineurium is a semipermeable membrane for water flow. Endoneurial hydrostatic pressure in nerves in isotonic Ringer exceeds bath pressure by about 7 mmHg. In Ringer made hypertonic by addition of sucrose, nerve volume and endoneurial pressure fall linearly in relation to 1/osmolality. The slope of the plot of pressure against volume provides a value for nerve compliance equal to 0.006 mm2/mmHg. Calculations based on the model of the nerve as an osmometer indicate that the nerve has an osmotically "inactive" volume equal to 0.19 mm3/mm, which is about 75% of the total volume of a nerve segment of unit length in normal Ringer. Perineurial hydraulic conductivity (Lp) equals 7.5 x 10(-13) cm3.s-1.dyn-1, a value characteristic of nonleaky epithelia. The perineurium is an elastic tissue with a constant modulus of elasticity equal to 3 x 10(6) dyn/cm2 when not markedly stretched and may limit nerve swelling under pathological conditions of nerve edema.

  • 146.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Loyd, Dan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Regurgitant flow through heart valves: a hydraulic model applicable to ultrasound Doppler measurements.1986Inngår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 24, nr 6, s. 643-646Artikkel i tidsskrift (Fagfellevurdert)
  • 147.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Pettersson, N-E
    n/a.
    Andersson, K
    n/a.
    Certification of Clinical Engineers in Sweden2009Inngår i: WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING, VOL 25, PT 12, ISSN 1680-0737, Vol. 25, nr 12, s. 430-431Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Swedish Society for Biomedical Engineering and Physics have certified clinical engineers since 1994. The certification is done on tow levels: Master of science and Bachelor of science. We have in total had 614 applications and certified 341 engineers We have certified a total of 341 persons of which 75 are at the master level and 266 at the bachelor level. We are pleased to note that through the years so many engineers have applied and have get a certification. The interest for applying was very large in the beginning but decreased after some years.

  • 148.
    Ask, Per
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Ressner, Marcus
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Janerot-Sjöberg, Birgitta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Jansson, Tomas
    Lunds universitet .
    Jurkonis, Rytis
    Kaunas University of Technology, Lithuania .
    Kvikliene, Adriana
    Kaunas University of Technology, Lithuania .
    Hoff, Lars
    Fac of Sience and Engineering, Vestfold University, Horten, Norge .
    Simulation of ultrasound contrast bubble response and the non-linear ultrasound field - combining with in vitro experiments2003Inngår i: New England Doppler Conference,2003, 2003Konferansepaper (Fagfellevurdert)
  • 149.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Skogh, Marcus
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Elektriska och mekaniska egenskaper hos EKG-elektroder1974Konferansepaper (Annet vitenskapelig)
  • 150.
    Ask, Per
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Skogh, Marcus
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Undersökning av EKG-elektroders elektriska och mekaniska långtidsegenskaper1974Rapport (Annet vitenskapelig)
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