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  • 201.
    Johansson, johannes
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Alonso, Fabiola
    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. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Patient-Specific Finite Element Simulations of Deep Brain Stimulation – Electrode Placement Using Leksell Coordinates2016Conference paper (Other academic)
    Abstract [en]

    Deep brain stimulation (DBS) is used for symptomatic treatment of movement disorders. Finite element method (FEM) simulations are useful for estimating the affected region around the electrode which can help determine the optimal target. This paper presents how the patient-specific electrode placement is simplified by the use of two Leksell coordinates in the postoperative imaging artefacts. The method is implemented in Comsol Multiphysics and exemplified by a patient-specific simulation in zona incerta (Zi).

  • 202.
    Johansson, Johannes
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Alonso, Fabiola
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Wårdell, Karin
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Simulering av aktiverade strukturer vid djup hjärnstimulering (DBS)2016Conference paper (Other academic)
    Abstract [sv]

    Djup hjärnstimulering är en metod för att lindra symptom från patologisk överaktivitet i hjärnanscentrala delar vid exempelvis Parkinsons sjukdom, dystoni och essentiell tremor. En litenelektrod implanteras kroniskt i det överaktiva området vilket störs ut med pulser från elektroden.I denna presentation beskrivs hur patientspecifika simuleringar med finita elementmetoden(FEM) kan utföras för att uppskatta vilka strukturer som aktiveras vid olikaelektrodinställningar. Patientens bilder från magnetresonanstomografi (MR) och datortomografikoregistreras och används för att bedöma elektrodens position och den elektriskaledningsförmågan i hjärnvävnaden kring den genom att klassificera vävnaden i grå och vithjärnvävnad samt cerebrospinalvätska och blod. Modeller för statisk strömledning baserade pådenna information och elektrodens inställningar skapas därefter i FEM-mjukvaran ComsolMultiphysics och simuleringar utförs. Aktiveringsområden baserade på den elektriskafältstyrkan och typiska diametrar på neuronernas axoner kan därefter överlagras med MR-bilderna för att bedöma vilka strukturer som påverkas. Detta möjliggör jämförelse med kliniskeffekt och eventuella biverkningar av stimuleringen hos patienterna. För närvarande undersökervi exempelvis DBS mot Tourettes syndrom och gör jämförelser mellan elektrodposition ochaccelerometermätningar vid DBS mot skakningar.

  • 203.
    Johansson, Johannes
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Blomstedt, P.
    Department of Neurosurgery University Hospital, Umeå, Sweden.
    Haj-Hosseini, Neda
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Bergenheim, A. T.
    Department of Neurosurgery University Hospital, Umeå, Sweden.
    Hariz, M. I.
    Department of Neurosurgery University Hospital, Umeå, Sweden.
    Eriksson, Ola
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Combined electric impedance and optical diffuse reflectance measurements for navigation aid in deep brain surgery2008In: XVIII Congress of the European Society for Stereotactic and Functional Neurosurgery,2008, 2008Conference paper (Other academic)
  • 204.
    Johansson, Johannes
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Blomstedt, Patric
    Neurokirurgiska kliniken Norrlands universitetssjukhus.
    Hariz, Marwan
    Institute of Neurology University College, London, UK.
    Bergenheim, Tommy
    Neurokirurgiska kliniken Norrlands universitetssjukhus.
    Eriksson, Ola
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Simultan jämförande mätning av elektrisk impedans och reflekterat ljus för guidning vid stereotakisk neurokirurgi2007In: Medicinteknikdagarna,2007, 2007Conference paper (Other academic)
  • 205.
    Johansson, Johannes D.
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Blomstedt, Patric
    Department of Neurosurgery, Norrland´s University Hospital, Umeå, Sweden.
    Haj-Hosseini, Neda
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Bergenheim, Tommy
    Department of Neurosurgery, Norrland´s University Hospital, Umeå, Sweden.
    Eriksson, Ola
    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.
    Combined diffuse light reflectance and electric impedance measurements for navigation aid in deep brain surgery2009In: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 87, no 2, p. 105-113Article in journal (Refereed)
    Abstract [en]

    Aim: The aim of this study is to investigate reflected light intensity combined with impedance for navigation aid during stereotactic neurosurgery.

    Methods: During creation of 21 trajectories for stereotactic implantation of deep brain stimulation electrodes in the globus pallidus internus or subthalamus (zona incerta or subthalamic nucleus), impedance at 512 kHz and reflected light intensity at 780 nm were measured continuously and simultaneously with a radio frequency electrode containing optical fibres. The signals were compared with anatomy determined from pre- and postoperative MRI and CT. The measurements were performed within minutes and signal analysis was done post-operatively.

    Results: Reflected light intensity was low from cortex, lateral ventricle, caudate nucleus and putamen. It was intermediate from globus pallidus and thalamus while it was high from subcortical white matter, internal capsule and the subthalamus. The electric impedance was less consistent but generally low in the cortex, intermediate in subcortical white matter, the putamen, the globus pallidus and the thalamus and high in the internal capsule and the subthalamus.

    Conclusion: Reflected light intensity and electric impedance give complementary information about passed tissue and the combination seems promising for navigation aid during stereotactic neurosurgery.

  • 206.
    Johansson, Johannes D.
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Eriksson, Ola
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wren, Joakim
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Comparison between a detailed and a simplified finite element model of radio-frequency lesioning in the brain2004In: 26th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, San Fransisco, USA, 2004, Vol. 4, p. 2510-2513Conference paper (Refereed)
    Abstract [en]

    A detailed and a simplified model of a lesioning electrode was made using the finite element method. 15 simulations of the lesioning procedure were performed for each model and the resulting lesion volumes were compared in order to investigate if the simplified model is adequate. The simplified model resulted in a very slight overestimation of the volume compared to the detailed model. It was thus concluded that the simplified model is adequate for simulations.

  • 207.
    Johansson, Johannes D
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Eriksson, Ola
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wren, Joakim
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Radio-frequency lesioning in brain tissue with coagulation-dependent thermal conductivity: modelling, simulation and analysis of parameter influence and interaction2006In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 44, no 9, p. 757-766Article in journal (Refereed)
    Abstract [en]

    Radio-frequency brain lesioning is a method for reducing e.g. symptoms of movement disorders. A small electrode is used to thermally coagulate malfunctioning tissue. Influence on lesion size from thermal and electric conductivity of the tissue, microvascular perfusion and preset electrode temperature was investigated using a finite-element model. Perfusion was modelled as an increased thermal conductivity in non-coagulated tissue. The parameters were analysed using a 24-factorial design (n = 16) and quadratic regression analysis (n = 47). Increased thermal conductivity of the tissue increased lesion volume, while increased perfusion decreased it since coagulation creates a thermally insulating layer due to the cessation of blood perfusion. These effects were strengthened with increased preset temperature. The electric conductivity had negligible effect. Simulations were found realistic compared to in vivo experimental lesions.

  • 208.
    Johansson, Johannes D.
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Eriksson, Ola
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wren, Joakim
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Health Sciences.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Simulations of radio-frequency lesions with varying brain electrode dimensions2005In: 13th Nordic Baltic conference biomedical engineering and medical physics, Umeå, Sweden, 2005, Vol. 9, p. 62-63Conference paper (Refereed)
    Abstract [en]

    Radio-frequency (RF) lesioning in the

    brain was simulated using the finite element method

    (FEM). Heating for 60 s with temperature control in

    order to keep the tip at 80 °C was simulated. Length,

    L, (2 – 4 mm) and diameter, D, (0.5 – 2.5 mm) of the

    electrode tip were varied and the resulting lesion

    volumes were used to calculate a regression model:

    Lesion Volume = – 13.1D + 15.7LD + 13.1D2 mm3.

    The results can be useful for electrode design and

    prediction of lesion size.

  • 209.
    Johansson, Johannes D.
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Fredriksson, Ingemar
    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.
    Eriksson, Ola
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Simulation of reflected light intensity changes during navigation and radio frequency lesioning in the brain2009In: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 14, no 044040Article in journal (Refereed)
    Abstract [en]

    An electrode with adjacent optical fibers for measurements during navigation and radio frequency lesioning in the brain was modeled for Monte Carlo simulations of light transport in brain tissue. Relative reflected light intensity at 780 nm, I780, from this electrode and probes with identical fiber configuration were simulated using the intensity from native white matter as reference. Models were made of homogeneousnative and coagulated gray, thalamus, and white matter as well as blood. Dual layermodels, including models with a layer of cerebrospinal fluid between the fibers andthe brain tissue, were also made. Simulated I780 was 0.16 for gray matter, 0.67 forcoagulate gray matter, 0.36 for thalamus, 0.39 for coagulated thalamus, unity forwhite matter, 0.70 for coagulated white matter and 0.24 for blood. Thalamic matterhas also been found to reflect more light than gray matter and less than white matterin clinical studies. In conclusion the reflected light intensity can be used todifferentiate between gray and white matter during navigation. Furthermore,coagulation of light gray tissue, such as the thalamus, might be difficult to detectusing I780, but coagulation in darker gray tissue should result in a rapid increase of I780.

  • 210.
    Johansson, Johannes D.
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wren, Joakim
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Impact of cysts during radio frequency (RF) lesioning in deep brain structures: a simulation and in-vitro study2007In: Journal of Neural Engineering, ISSN 1741-2560, E-ISSN 1741-2552, Vol. 4, no 2, p. 87-95Article in journal (Refereed)
    Abstract [en]

    Radiofrequency lesioning of nuclei in the thalamus or the basal ganglia can be used to reduce symptoms caused by e.g. movement disorders such as Parkinson's disease. Enlarged cavities containing cerebrospinal fluid (CSF) are commonly present in the basal ganglia and tend to increase in size and number with age. Since the cavities have different electrical and thermal properties compared with brain tissue, it is likely that they can affect the lesioning process and thereby the treatment outcome. Computer simulations using the finite element method and in vitro experiments have been used to investigate the impact of cysts on lesions' size and shape. Simulations of the electric current and temperature distributions as well as convective movements have been conducted for various sizes, shapes and locations of the cysts as well as different target temperatures. Circulation of the CSF caused by the heating was found to spread heat effectively and the higher electric conductivity of the CSF increased heating of the cyst. These two effects were together able to greatly alter the resulting lesion size and shape when the cyst was in contact with the electrode tip. Similar results were obtained for the experiments.

  • 211.
    Johansson, Johannes D.
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Health Sciences.
    Zerbinati, Alice
    Politecnico di Torino, Turin, Italy.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Health Sciences.
    Diffuse Reflectance Spectroscopy During Experimental Radio Frequency Ablation2008In: 14th Nordic-Baltic Conference on Biomedical Engineering and Medical Physics: NBC 2008 16–20 June 2008 Riga, Latvia / [ed] Alexei Katashev, Yuri Dekhtyar, Janis Spigulis, Heidelberg: Springer Berlin/Heidelberg, 2008, p. 371-374Chapter in book (Refereed)
    Abstract [en]

    The aim of the study was to investigate the spectral changes during heating and to estimate threshold temperatures for initiation of the thermal coagulation. A brain electrode with optical fibers was used to generate lesions in ex-vivo porcine white and gray matter as well as in fat and meat from pork chop. Radio frequency ablation (60 s, 48–90 °C, steps of 2-10 °C) was performed while simultaneous spectroscopy measurements were made in the range 490–900 nm.

    The optical signal recorded from porcine gray and white brain matter was unstable with the reflected light intensity fluctuating a lot. Nevertheless an abrupt increase in light intensity during coagulation in gray matter was found at 48 ± 6 °C (n = 21), probably indicating onset of coagulation. The reflected light intensity from white matter showed no consistent behavior during coagulation.

    The results for pork chop meat and fat were considerably more consistent. The reflected light intensity from pork chop meat stayed stable up to a mean temperature of 42.5 ± 3.5 °C (n = 11). Above this temperature it abruptly increased for all wavelengths. The reflected light intensity from pork chop fat dropped over all wavelengths immediately as the temperature increased and remained low as the fat cooled (n = 8).

    In conclusion diffuse reflectance spectroscopy appears to be suitable to detect onset of coagulation in muscle tissue and gray matter. The estimated initiation temperature of coagulation varied and was dependent on tissue type.

  • 212.
    Johansson, Johannes
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Eriksson, O.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    A system for optical guidance during stereotactic neurosurgery2010Conference paper (Refereed)
  • 213.
    Johansson, Johannes
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Eriksson, O.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Models for computer simulations of RF lesions in brain tissue2002Conference paper (Refereed)
  • 214.
    Johansson, Johannes
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Eriksson, Ola
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wren, Joakim
    Linköping University, Department of Mechanical Engineering.
    Loyd, Dan
    Linköping University, Department of Mechanical Engineering.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    FEM-modell för termisk koagulering i hjärnvävnad2003In: Svenska lakaresallskapets riksstamma,2003, 2003, p. 242-242Conference paper (Other academic)
  • 215.
    Johansson, Johannes
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Fredriksson, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Eriksson, Ola
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Simulering av ljusreflektion i hjärnan under navigation och radiofrekvensablation2008In: Medicinteknikdagarna 2008,2008, 2008, p. 70-70Conference paper (Other academic)
  • 216.
    Johansson, Johannes
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Fredriksson, Ingemar
    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.
    Eriksson, Ola
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Monte Carlo simulations of reflected light intensity for navigation in the brain2009Conference paper (Other academic)
  • 217.
    Johansson, Johannes
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Loyd, Dan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wren, Joakim
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    The influence of CSF-filled cavities on radio-frequency lesions - a simulation study2006In: Congress of the European Society for Stereotactic and Functional Neurosurgery,2006, New York: Springer , 2006Conference paper (Other academic)
  • 218.
    Johansson, Johannes
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Wren, Joakim
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Eriksson, O.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wårdell, Karin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Teoretisk och experimentell undersökning av värmekoagulation med radiofrekvent ström i hjärna2005Conference paper (Refereed)
  • 219.
    Johansson, Johannes
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wren, Joakim
    Linköping University, Department of Mechanical Engineering.
    Eriksson, Ola
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Loyd, Dan
    Linköping University, Department of Mechanical Engineering.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Investigation of brain RF-lesion size by finite element simulations2004In: European Society for Stereotactic and Functional Neurosurgery ESSFN,2004, Wien: Springer Verlag , 2004, p. 932-932Conference paper (Other academic)
  • 220.
    Johansson, Johannes
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wren, Joakim
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Loyd, Dan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Eriksson, Ola
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Konvektiva flöden och deras termiska inverkan vid Radiofrekvenslesionering i hjärna2006In: Medicinteknikdagarna 2006,2006, 2006Conference paper (Other academic)
    Abstract [en]

       

  • 221.
    Johansson, Johannes
    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.
    Intracerebral quantitative chromophore estimation from reflectance spectra captured during deep brain stimulation implantation2013In: Journal of Biophotonics, ISSN 1864-063X, E-ISSN 1864-0648, Vol. 6, no 5, p. 435-445Article in journal (Refereed)
    Abstract [en]

    Quantification of blood fraction (fblood), blood oxygenation (S), melanin, lipofuscin and oxidised and reduced Cytochrome aa 3 and c was done from diffuse reflectance spectra captured in cortex, white matter, globus pallidus internus (GPi) and subthalamus during stereotactic implantations of 29 deep brain stimulation (DBS) electrodes with the aim of investigating whether the chromophores can give physiological information about the targets for DBS. Double-sided Mann-Whitney U -tests showed more lipofuscin in GPi compared to white matter and subthalamus (p < 0.05). Compared to the other structures, fbloodwas significantly higher in cortex (p < 0.05) and S lower in GPi (p < 0.05). Median values and range for fblood were 1.0 [0.2–6.0]% in the cortex, 0.3 [0.1–8.2]% in white matter, 0.2 [0.1–0.8]% in the GPi and 0.2 [0.1–11.7]% in the subthalamus. Corresponding values for S was 20 [0–81]% in the cortex, 29 [0–78]% in white matter, 0 [0–0]% in the GPi and 0 [0–92]% in the subthalamus. In conclusion, the measurements indicate very low oxygenation and blood volume for DBS patients, especially in the GPi. It would be of great interest to investigate whether this is due to the disease, the normal situation or an artefact of doing invasive measurements.

  • 222.
    Jonasson, Hanna
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Model-based quantitative assessment of skin microcirculatory blood flow and oxygen saturation2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The microcirculation, involving the smallest vessels in the body, is where the oxygen transport to all tissue occurs. Evaluating microcirculatory parameters is, therefore, important and involves the quantification of oxygen content of red blood cells (RBCs), the amount of RBCs and their speed.

    Diffuse reflectance spectroscopy (DRS) can be used to estimate blood oxygen saturation and fraction of RBCs in tissue since oxygenated and deoxygenated blood have different light absorption characteristics. By illuminating the skin with white light and detecting the spectrum of the backscattered light, tissue absorption and scattering can be assessed. Laser Doppler flowmetry (LDF) is a technique to measure blood flow in tissue. When laser light encounter moving objects in tissue, i.e. RBCs, the light is Doppler shifted, which can be detected and used to calculate tissue perfusion (the fraction of moving RBCs times their speed). With a small distance between light source and detector, both techniques measure superficially where most vessels are microcirculatory vessels. Photon transport in tissue can be simulated with Monte Carlo techniques and the simulations form the basis of modeled DRS and LDF spectra. The estimated microcirculatory parameters are given by the model that best describe measured DRS and LDF data.

    This thesis describes the development and the evaluation of an optical method to simultaneously measure oxygen saturation, RBC tissue fraction and speed resolved perfusion in absolute units by integrating DRS and LDF. By combining DRS and LDF into one system with a common tissue model, the two modalities can benefit from each other’s strengths. Different calibration methods and model assumptions for the system were evaluated in optical phantoms and in skin measurements. A simple calibration method with two detector distances for DRS was found adequate to accurately estimate absorption and scattering in optical phantoms. It was also necessary to model blood located in vessels, rather than homogeneously distributed in the skin, to obtain accurate parameter estimates. The system was evaluated in healthy subjects during standard provocations, where the parameters were in agreement with other studies and followed an expected pattern during the provocations. In patients with diabetes type 2, tissue fraction of RBCs and nutritive blood flow were reduced in baseline compared to healthy controls. These differences were not related to prevalence of microalbuminuria, a marker sign of microvascular complications in the kidneys.

    A combined system with DRS and LDF enables a more comprehensive assessment of the microcirculation by measuring oxygen saturation, RBC tissue fraction and speed resolved perfusion simultaneously and in absolute units. This system has clinical potential to assist in the evaluation of the microcirculation both in healthy and diseased individuals.

    List of papers
    1. Can a one-layer optical skin model including melanin and inhomogeneously distributed blood explain spatially resolved diffuse reflectance spectra?
    Open this publication in new window or tab >>Can a one-layer optical skin model including melanin and inhomogeneously distributed blood explain spatially resolved diffuse reflectance spectra?
    2011 (English)In: Optical Tomography and Spectroscopy of Tissue IX / [ed] Robert R. Alfano; Bruce J. Tromberg; Arjun G. Yodh; Mamoru Tamura; Eva M. Sevick-Muraca, SPIE - International Society for Optical Engineering, 2011, Vol. 7896, p. 78962Y-78962Y-9Conference paper, Published paper (Other academic)
    Abstract [en]

    Model based analysis of calibrated diffuse reflectance spectroscopy can be used for determining oxygenation and concentration of skin chromophores. This study aimed at assessing the effect of including melanin in addition to hemoglobin (Hb) as chromophores and compensating for inhomogeneously distributed blood (vessel packaging), in a single-layer skin model. Spectra from four humans were collected during different provocations using a twochannel fiber optic probe with source-detector separations 0.4 and 1.2 mm. Absolute calibrated spectra using data from either a single distance or both distances were analyzed using inverse Monte Carlo for light transport and Levenberg-Marquardt for non-linear fitting. The model fitting was excellent using a single distance. However, the estimated model failed to explain spectra from the other distance. The two-distance model did not fit the data well at either distance. Model fitting was significantly improved including melanin and vessel packaging. The most prominent effect when fitting data from the larger separation compared to the smaller separation was a different light scattering decay with wavelength, while the tissue fraction of Hb and saturation were similar. For modeling spectra at both distances, we propose using either a multi-layer skin model or a more advanced model for the scattering phase function.

    Place, publisher, year, edition, pages
    SPIE - International Society for Optical Engineering, 2011
    Series
    Proceedings of SPIE - International Society for Optical Engineering, ISSN 0277-786X, E-ISSN 1996-756X ; 7896
    Keywords
    diffuse reflectance spectroscopy, light transport, Monte Carlso simulation, tissue moedeling, vessel packaging, skin
    National Category
    Medical Laboratory and Measurements Technologies
    Identifiers
    urn:nbn:se:liu:diva-81240 (URN)10.1117/12.873134 (DOI)
    Conference
    Optical Tomography and Spectroscopy of Tissue IX Conference, San Francisco, California, January 22, 2011
    Available from: 2012-09-14 Created: 2012-09-10 Last updated: 2017-02-10Bibliographically approved
    2. Inverse Monte Carlo for estimation of scattering and absorption in liquid optical phantoms
    Open this publication in new window or tab >>Inverse Monte Carlo for estimation of scattering and absorption in liquid optical phantoms
    2012 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, no 11, p. 12233-12246Article in journal (Refereed) Published
    Abstract [en]

    A spectroscopic probe with multiple detecting fibers was used for quantifying absorption and scattering in liquid optical phantoms. The phantoms were mixtures of Intralipid and red and blue food dyes. Intensity calibration for the detecting fibers was undertaken using either a microsphere suspension (absolute calibration) or a uniform detector illumination (relative calibration between detectors). Two different scattering phase functions were used in an inverse Monte Carlo algorithm. Data were evaluated for residual spectra (systematic deviations and magnitude) and accuracy in estimation of scattering and absorption. Spectral fitting was improved by allowing for a 10% intensity relaxation in the optimization algorithm. For a multi-detector setup, non-systematic residual spectrum was only found using the more complex Gegenbauer-kernel phase function. However, the choice of phase function did not influence the accuracy in the estimation of absorption and scattering. Similar estimation accuracy as in the multi-detector setup was also obtained using either two relative calibrated detectors or one absolute calibrated detector at a fiber separation of 0.46 mm.

    Place, publisher, year, edition, pages
    Optical Society of America, 2012
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-78815 (URN)10.1364/OE.20.012233 (DOI)000304403100070 ()
    Note

    Funding Agencies|VINNOVA||Perimed AB|2008-00149|ResearchGrow program|2011-03074|European Union||Linkoping University through the Center for Excellence NIMED-CBDP (Center for Biomedical Data Processing)||

    Available from: 2012-06-21 Created: 2012-06-21 Last updated: 2017-12-07Bibliographically approved
    3. Microcirculation assessment using an individualized model for diffuse reflectance spectroscopy and conventional laser Doppler flowmetry
    Open this publication in new window or tab >>Microcirculation assessment using an individualized model for diffuse reflectance spectroscopy and conventional laser Doppler flowmetry
    Show others...
    2014 (English)In: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 19, no 5, p. 057002-Article in journal (Refereed) Published
    Abstract [en]

    Microvascular assessment would benefit from co-registration of blood flow and hemoglobin oxygenation dynamics during stimulus response tests. We used a fiber-optic probe for simultaneous recording of white light diffuse reflectance (DRS; 475-850 nm) and laser Doppler flowmetry (LDF; 780 nm) spectra at two source-detector distances (0.4 and 1.2 mm). An inverse Monte Carlo algorithm, based on a multiparameter three-layer adaptive skin model, was used for analyzing DRS data. LDF spectra were conventionally processed for perfusion. The system was evaluated on volar forearm recordings of 33 healthy subjects during a 5-min systolic occlusion protocol. The calibration scheme and the optimal adaptive skin model fitted DRS spectra at both distances within 10%. During occlusion, perfusion decreased within 5 s while oxygenation decreased slowly (mean time constant 61 s; dissociation of oxygen from hemoglobin). After occlusion release, perfusion and oxygenation increased within 3 s (inflow of oxygenized blood). The increased perfusion was due to increased blood tissue fraction and speed. The supranormal hemoglobin oxygenation indicates a blood flow in excess of metabolic demands. In conclusion, by integrating DRS and LDF in a fiber-optic probe, a powerful tool for assessment of blood flow and oxygenation in the same microvascular bed has been presented.

    Place, publisher, year, edition, pages
    SPIE - International Society for Optical Engineering, 2014
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-107715 (URN)10.1117/1.JBO.19.5.057002 (DOI)000338334600033 ()24788373 (PubMedID)
    Available from: 2014-06-19 Created: 2014-06-19 Last updated: 2017-12-05Bibliographically approved
    4. Oxygen saturation, red blood cell tissue fraction and speed resolved perfusion — A new optical method for microcirculatory assessment
    Open this publication in new window or tab >>Oxygen saturation, red blood cell tissue fraction and speed resolved perfusion — A new optical method for microcirculatory assessment
    Show others...
    2015 (English)In: Microvascular Research, ISSN 0026-2862, E-ISSN 1095-9319, Vol. 102, p. 70-77Article in journal (Refereed) Published
    Abstract [en]

    We have developed a new fiber-optic system that combines diffuse reflectance spectroscopy (DRS) and laser Doppler Flowmetry (LDF) for a multi-modal assessment of the microcirculation. Quantitative data is achieved with an inverse Monte Carlo algorithm based on an individually adaptive skin model. The output parameters are calculated from the model and given in absolute units: hemoglobin oxygen saturation (%), red blood cell (RBC) tissue fraction (%), and the speed resolved RBC perfusion separated into three speed regions; 0–1 mm/s, 1–10 mm/s and above 10 mm/s (% mm/s). The aim was to explore microcirculatory parameters using the new optical method, integrating DRS and LDF in a joint skin model, during local heating of the dorsal foot and venous and arterial occlusion of the forearm in 23 healthy subjects (age 20–28 years). There were differences in the three speed regions in regard to blood flow changes due to local heating, where perfusion for high speeds increased the most. There was also a high correlation between changes in oxygenation and changes in perfusion for higher speeds. Oxygen saturation at baseline was 44% on foot, increasing to 83% at plateau after heating. The larger increase in perfusion for higher speeds than for lower speeds together with the oxygenation increase during thermal provocation, shows a local thermoregulatory blood flow in presumably arteriolar dermal vessels. In conclusion, there are improved possibilities to assess microcirculation using integrated DRS and LDF in a joint skin model by enabling both oxygenation and speed resolved blood flow assessment simultaneously and in the same skin site. Output parameters in absolute units may also yield new insights about the microcirculatory system.

    Place, publisher, year, edition, pages
    Academic Press, 2015
    Keywords
    Diffuse reflectance spectroscopy; Hemoglobin oxygen saturation; Laser Doppler flowmetry; Microcirculation; Skin blood flow
    National Category
    Medical Laboratory and Measurements Technologies
    Identifiers
    urn:nbn:se:liu:diva-121774 (URN)10.1016/j.mvr.2015.08.006 (DOI)000362310700010 ()26279347 (PubMedID)
    Note

    Funding text:  VINNOVA (Swedens innovation agency); Perimed AB through the SamBIO research collaboration program [2008-00149]; Research&Grow program (VINNOVA) [2011-03074]; NovaMedTech - European Union Regional Development Fund [68737, 160382]

    Available from: 2015-10-05 Created: 2015-10-05 Last updated: 2017-12-01
  • 223.
    Jonasson, Hanna
    et al.
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Bergstrand, Sara
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Nyström, Fredrik H
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Endocrinology.
    Länne, Toste
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Thoracic and Vascular Surgery.
    Östgren, Carl Johan
    Linköping University, Department of Medical and Health Sciences, Division of Community Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Primary Care Center, Primary Health Care Center Ödeshög.
    Bjarnegård, Niclas
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences.
    Fredriksson, Ingemar
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering. Perimed AB, Sweden.
    Larsson, Marcus
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Strömberg, Tomas
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Skin microvascular endothelial dysfunction is associated with type 2 diabetes independently of microalbuminuria and arterial stiffness2017In: Diabetes & Vascular Disease Research, ISSN 1479-1641, E-ISSN 1752-8984, Vol. 14, no 4, p. 363-371, article id UNSP 1479164117707706Article in journal (Refereed)
    Abstract [en]

    Skin and kidney microvascular functions may be affected independently in diabetes mellitus. We investigated skin microcirculatory function in 79 subjects with diabetes type 2, where 41 had microalbuminuria and 38 not, and in 41 age-matched controls. The oxygen saturation, fraction of red blood cells and speed-resolved microcirculatory perfusion (% red blood cells x mm/s) divided into three speed regions: 0-1, 1-10 and above 10 mm/s, were assessed during baseline and after local heating of the foot with a new device integrating diffuse reflectance spectroscopy and laser Doppler flowmetry. Arterial stiffness was assessed as carotid-femoral pulse wave velocity. Subjects with diabetes and microalbuminuria had significantly higher carotid-femoral pulse wave velocity compared to subjects without microalbuminuria and to controls. The perfusion for speeds 0-1 mm/s and red blood cell tissue fraction were reduced in subjects with diabetes at baseline and after heating, independent of microalbuminuria. These parameters were correlated to HbA1c. In conclusion, the reduced nutritive perfusion and red blood cell tissue fraction in type 2 diabetes were related to long-term glucose control but independent of microvascular changes in the kidneys and large-vessel stiffness. This may be due to different pathogenic pathways in the development of nephropathy, large-vessel stiffness and cutaneous microvascular impairment.

  • 224.
    Jonasson, Hanna
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Fredriksson, Ingemar
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology. Perimed AB, Järfälla-Stockholm, Sweden .
    Larsson, Marcus
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Strömberg, Tomas
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Assessment of the microcirculation using combined model based diffuse reflectance spectroscopy and laser Doppler flowmetry2015In: 16th Nordic-Baltic Conference on Biomedical Engineering: 16. NBC & 10. MTD 2014 joint conferences. October 14-16, 2014, Gothenburg, Sweden, Springer, 2015, p. 52-54Conference paper (Refereed)
    Abstract [en]

    By using a combined inverse model for diffuse reflectance spectroscopy (DRS) and laser Doppler flowmetry (LDF) the tissue fraction of red blood cells (RBCs), their oxygenation and speed-resolved perfusion are estimated in absolute units. DRS spectra (450 to 850 nm) are measured at two source-detector distances; 0.4 and 1.2 mm. LDF spectra are measured at 1.2 mm, integrated in the same fiber-optic probe. Inverse Monte Carlo technique and an adaptive tissue model is used to quantify the microcirculatory parameters. Measurements were done during venous occlusion of the tissue. The model fitting yields a good spectral fit for the two DRS spectra and the LDF spectrum. The physiological responses regarding for example which speed regions respond to provocations follows a priori expectations. The combined model gives quantitative measures of RBC tissue fraction, oxygenation and speed resolved perfusion from the same sampling volume which gives new opportunities to interpret data.

  • 225.
    Jonasson, Hanna
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Fredriksson, Ingemar
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. Perimed AB, Datavägen 9A, 175 43 Järfälla, Stockholm, Sweden.
    Pettersson, Anders
    Perimed AB, Datavägen 9a, 175 26 Järfälla-Stockholm.
    Larsson, Marcus
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Strömberg, Tomas
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Oxygen saturation, red blood cell tissue fraction and speed resolved perfusion — A new optical method for microcirculatory assessment2015In: Microvascular Research, ISSN 0026-2862, E-ISSN 1095-9319, Vol. 102, p. 70-77Article in journal (Refereed)
    Abstract [en]

    We have developed a new fiber-optic system that combines diffuse reflectance spectroscopy (DRS) and laser Doppler Flowmetry (LDF) for a multi-modal assessment of the microcirculation. Quantitative data is achieved with an inverse Monte Carlo algorithm based on an individually adaptive skin model. The output parameters are calculated from the model and given in absolute units: hemoglobin oxygen saturation (%), red blood cell (RBC) tissue fraction (%), and the speed resolved RBC perfusion separated into three speed regions; 0–1 mm/s, 1–10 mm/s and above 10 mm/s (% mm/s). The aim was to explore microcirculatory parameters using the new optical method, integrating DRS and LDF in a joint skin model, during local heating of the dorsal foot and venous and arterial occlusion of the forearm in 23 healthy subjects (age 20–28 years). There were differences in the three speed regions in regard to blood flow changes due to local heating, where perfusion for high speeds increased the most. There was also a high correlation between changes in oxygenation and changes in perfusion for higher speeds. Oxygen saturation at baseline was 44% on foot, increasing to 83% at plateau after heating. The larger increase in perfusion for higher speeds than for lower speeds together with the oxygenation increase during thermal provocation, shows a local thermoregulatory blood flow in presumably arteriolar dermal vessels. In conclusion, there are improved possibilities to assess microcirculation using integrated DRS and LDF in a joint skin model by enabling both oxygenation and speed resolved blood flow assessment simultaneously and in the same skin site. Output parameters in absolute units may also yield new insights about the microcirculatory system.

  • 226.
    Kalman, Sigga
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Linderfalk, C
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Eintrei, Christina
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Intensive Care UHL.
    Lisander, Björn
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology.
    Differential effect on vasodilatation and pain after intradermal capsaicin in humans during decay of intravenous regional anesthesia with mepivacaine1998In: Regional anesthesia and pain medicine, ISSN 1098-7339, E-ISSN 1532-8651, Vol. 23, no 4, p. 402-408Article in journal (Refereed)
  • 227.
    Karlsson, Daniel M G
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Ahn, Henrik Casimir
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Thoracic Surgery. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Lönn, Urban
    Thoraxklin US .
    Wårdell, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Analysis of laser Doppler flowmetry signals during the cardiac cyclle of the beating calf heart2000In: Abstracts 21st European Conference on Microcirculation, S. Karger, 2000, Vol. 37, p. 1-85, article id Suppl. 1Conference paper (Refereed)
  • 228.
    Karlsson, Daniel M G
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Larsson, Marcus
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Strömberg, Tomas
    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.
    Influence of tissue movements on laser Doppler perfusion imaging2002In: Proceedings of SPIE Volume 4624: Optical Diagnostics and Sensing of Biological Fluids and Glucose and Cholesterol Monitoring II / [ed] Alexander V. Priezzhev; Gerard L. Cote, SPIE - International Society for Optical Engineering, 2002, Vol. 4624, p. 106-114Conference paper (Other academic)
    Abstract [en]

    The microvascular perfusion can be measured using laser Doppler blood flowmetry (LDF), a technique sensitive to the concentration of moving blood cells and their velocity. However, movements of the tissue itself can cause artifacts in the perfusion readings. In a clinical situation, these movement induced artifacts may arise from patient movements or from movements of internal organs e.g. the intestines or the beating heart. Therefore, we have studied how a well-controlled tissue movement affects the LDF signals during different flow conditions and for different surface structures. Tissue perfusion was recorded non-touch in one point using a laser Doppler perfusion imager. During the measurements the object was placed on a shaker that generated the movement (both horizontal and vertical). Measurements were carried out both on DELRIN« (polyacetal plastic) and the fingertip, for a wide range of velocities (0-3 cm/s). The influence of the microvascular perfusion was evaluated by occluding the brachial artery as well as blood emptying the finger and by using a flow model. The LDF signals were correlated to the movement. In vivo measurements showed that velocities above 0.8 cm/s gave a significant contribution to the perfusion signal. Corresponding velocities for the DELRIN« piece were higher (1.4 - 2.6 cm/s), and dependent on the surface structures and reflecting properties. By reducing the amount of specular reflection the movement influence was substantially lowered.

  • 229.
    Karlsson, Hanna
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Fredriksson, Ingemar
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Larsson, Marcus
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Strömberg, Tomas
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Inverse Monte Carlo for estimation of scattering and absorption in liquid optical phantoms2012In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, no 11, p. 12233-12246Article in journal (Refereed)
    Abstract [en]

    A spectroscopic probe with multiple detecting fibers was used for quantifying absorption and scattering in liquid optical phantoms. The phantoms were mixtures of Intralipid and red and blue food dyes. Intensity calibration for the detecting fibers was undertaken using either a microsphere suspension (absolute calibration) or a uniform detector illumination (relative calibration between detectors). Two different scattering phase functions were used in an inverse Monte Carlo algorithm. Data were evaluated for residual spectra (systematic deviations and magnitude) and accuracy in estimation of scattering and absorption. Spectral fitting was improved by allowing for a 10% intensity relaxation in the optimization algorithm. For a multi-detector setup, non-systematic residual spectrum was only found using the more complex Gegenbauer-kernel phase function. However, the choice of phase function did not influence the accuracy in the estimation of absorption and scattering. Similar estimation accuracy as in the multi-detector setup was also obtained using either two relative calibrated detectors or one absolute calibrated detector at a fiber separation of 0.46 mm.

  • 230.
    Karlsson, Hanna
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Fredriksson, Ingemar
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Larsson, Marcus
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Strömberg, Tomas
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Kvantitativa mätningar av mikrocirkulatoriska parametrar med optiska tekniker och en realistisk hudmodell2011Conference paper (Other academic)
  • 231.
    Karlsson, Hanna
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Fredriksson, Ingemar
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Perimed AB, Järfälla, Sweden.
    Larsson, Marcus
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Strömberg, Tomas
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Speed resolved assessment of the microcirculation using combined model based diffuse reflectance spectroscopy and laser Doppler flowmetry2014Conference paper (Other academic)
  • 232.
    Karlsson, Hanna
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Pettersson, Anders
    Perimed AB, Järfälla-Stockholm.
    Larsson, Marcus
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Strömberg, Tomas
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Can a one-layer optical skin model including melanin and inhomogeneously distributed blood explain spatially resolved diffuse reflectance spectra?2011In: Optical Tomography and Spectroscopy of Tissue IX / [ed] Robert R. Alfano; Bruce J. Tromberg; Arjun G. Yodh; Mamoru Tamura; Eva M. Sevick-Muraca, SPIE - International Society for Optical Engineering, 2011, Vol. 7896, p. 78962Y-78962Y-9Conference paper (Other academic)
    Abstract [en]

    Model based analysis of calibrated diffuse reflectance spectroscopy can be used for determining oxygenation and concentration of skin chromophores. This study aimed at assessing the effect of including melanin in addition to hemoglobin (Hb) as chromophores and compensating for inhomogeneously distributed blood (vessel packaging), in a single-layer skin model. Spectra from four humans were collected during different provocations using a twochannel fiber optic probe with source-detector separations 0.4 and 1.2 mm. Absolute calibrated spectra using data from either a single distance or both distances were analyzed using inverse Monte Carlo for light transport and Levenberg-Marquardt for non-linear fitting. The model fitting was excellent using a single distance. However, the estimated model failed to explain spectra from the other distance. The two-distance model did not fit the data well at either distance. Model fitting was significantly improved including melanin and vessel packaging. The most prominent effect when fitting data from the larger separation compared to the smaller separation was a different light scattering decay with wavelength, while the tissue fraction of Hb and saturation were similar. For modeling spectra at both distances, we propose using either a multi-layer skin model or a more advanced model for the scattering phase function.

  • 233.
    Kircher, Albert
    et al.
    Technical University Graz Austria.
    Antonsson, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Babic, Ankica
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Medical Informatics.
    Ahn, Henrik Casimir
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Thoracic Surgery. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Quantitative data analysis for exploring outcomes in cardiac surgery1999In: Medical Informatics Europe99,1999, Amsterdam: IOS Press , 1999, p. 457-Conference paper (Refereed)
  • 234.
    Kircher, Albert
    et al.
    Technical University Graz Austria.
    Granfeldt, Hans
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Thoracic Surgery. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Babic, Ankica
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Medical Informatics.
    Antonsson, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Lönn, Urban
    Hjärtcentrum, Universitetssjukhuset Linköping.
    Ahn, Henrik Casimir
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Thoracic Surgery. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Knowledge representation forms for data mining methodologies as applied in thoracic surgery2000In: AMIA,2000, Philadelphia: Hanley & Belfus Inc , 2000, p. 428-432Conference paper (Refereed)
    Abstract [en]

    Typical ways of disseminating and using results of clinical research are scientific journals and reports. Presentation forms are condensed and comprehensible mainly to the experts following the specific topics. A vast amount of information remains unutilized due to the complex form of presenting the knowledge. Subject of this research is to explore possibilities of representation and also visualization of the results obtained using data mining methodologies. The intention is to formulate more than scientific ways to communicate facts that are of interest for the clinicians, medical students and even patients. Internet technologies as already widely established media support knowledge representation forms such as hypertext documents and structured knowledge components. The "Assist Me" decision support system for surgical treatment of cardiac patients integrates several forms of data mining and representation methodologies. We are showing a feasibility study in which scientific outcomes were forwarded to a broad group of potential users.

  • 235.
    Kistler, Benjamin
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology. Institute for Medical ans Analytical Technologies, University of Northwestern Switzerland.
    Development of a tissue-like protoporphyrin IX fluorescence phantom and performance of characterisation experiments2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Background and Objective: Fluorescence spectroscopy is a potential tool for brain tumour resection surgery. The main advantages of fluorescence spectroscopy are the objective fluorescence detection, possibility to quantify the signals and high sensitivity for instance to distinguish between healthy and neoplastic tissue. This distinction is a difficult task attributed to the diffuse growth pattern of brain tumour. A low dose of 5- aminolevulinic acid (5- ALA) is given orally to the patient. 5- ALA promotes accumulation of protporphyrin IX (PpIX) in the tumour cells which is a fluorescing substance. To measure the fluorescence emission the neurosurgeon examines the brain tissue with the help of an optical probe and spectroscopy system developed at the Department of Biomedical Engineering at Linköping University. The aim of this study was to develop an optical phantom which mimics brain tumour tissue. The phantom allows measuring and performing characterisation experiments in a controlled environment.

    Material and methods: To develop the tissue simulating phantom black ink and 20 % intralipid was used to obtain the optical properties of high grade glioma brain tumour. The optical properties of each substance were measured with collimated transmission spectroscopy and compared to the data reported in the literature. Agar gel was used to obtain similar photobleaching properties of tissue. Different PpIX concentrations were added to the phantom and fluorescence characterisation measurements were performed. Fluorescence quantification and the photobleaching as a function of concentration were investigated. An algorithm was established to predict the fluorescence concentration in the phantom based on the photobleaching decay characteristics.

    Results: An optical phantom with an error of ± 4 % was developed for the specified wavelength. The fluorescence ratio measurements showed a power and integration time independent relationship while they were linearly correlated (R= 0.79) with the PpIX concentration which could be quantified with a resolution of 4 μg ml-1. The fluorescence ratio values showed among the concentrations significant differences (p < 0.001) by using the Kruskal-Wallis. Three parameters of laser light pulsation, initial concentration of the fluorophore and excitation power affected the photobleaching proportionally. The developed algorithm can predict the fluorophore concentration in the phantom with an error of 9.2 %. The decay times for 63 % for loss of the initial intensity in the phantom (9 s - 43 s) were comparable with clinical data (19 s - 39 s). With the assumption that the photobleaching characteristics were the same in brain tumour tissue as in the phantom an already photobleached clinical measurement was reconstructed and the initial PpIX concentration was predicted.

    Conclusion: This study provides insight into a detailed development process of a brain tumour simulating optical phantom. The fluorescence ratio measurements showed a significant difference (p < 0.001) among different PpIX concentrations. Furthermore, the fluorescence ratio measurements showed a power and integration time independent linear relationship (R= 0.79) to quantify the PpIX concentration with a resolution of 4 μg ml-1. Additionally, main excitation parameters which affected the photobleaching kinetics in vivo were investigated in the phantom. The developed method to predict the fluorescence concentration in the phantom, based on the photobleaching measurements, was feasible to predict the initial intensity from a clinical measurements in a reasonable range but further investigations are required.

  • 236.
    Koulikovska, Marina
    et al.
    Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Ophthalmology in Linköping. Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences.
    Rafat, Mehrdad
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Medicine and Health Sciences. LinkoCare Life Sciences AB, Linköping, Sweden.
    Petrovski, Goran
    University of Debrecen, Debrecen, Hungary; University of Szeged, Szeged, Hungary.
    Veréb, Zoltán
    University of Debrecen, Debrecen, Hungary; University of Szeged, Szeged, Hungary.
    Akhtar, Saeed
    Department of Optometry, College of Applied Medicine, King Saud University, Riyadh, Saudi Arabia.
    Fagerholm, Per
    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 Ophthalmology in Linköping.
    Lagali, Neil
    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 Ophthalmology in Linköping.
    Enhanced Regeneration of Corneal Tissue Via a Bioengineered Collagen Construct Implanted by a Nondisruptive Surgical Technique2015In: Tissue Engineering. Part A, ISSN 1937-3341, E-ISSN 1937-335X, Vol. 21, no 5-6, p. 1116-1130Article in journal (Refereed)
    Abstract [en]

    Severe shortage of donor corneas for transplantation, particularly in developing countries, has prompted the advancement of bioengineered tissue alternatives. Bioengineered corneas that can withstand transplantation while maintaining transparency and compatibility with host cells, and that are additionally amenable to standardized low-cost mass production are sought. In this study, a bioengineered porcine construct (BPC) was developed to function as a biodegradable scaffold to promote corneal stromal regeneration by host cells. Using high-purity medical-grade type I collagen, high 18% collagen content and optimized EDC-NHS cross-linker ratio, BPCs were fabricated into hydrogel corneal implants with over 90% transparency and four-fold increase in strength and stiffness compared with previous versions. Remarkably, optical transparency was achieved despite the absence of collagen fibril organization at the nanoscale. In vitro testing indicated that BPC supported confluent human epithelial and stromal-derived mesenchymal stem cell populations. With a novel femtosecond laser-assisted corneal surgical model in rabbits, cell-free BPCs were implanted in vivo in the corneal stroma of 10 rabbits over an 8-week period. In vivo, transparency of implanted corneas was maintained throughout the postoperative period, while healing occurred rapidly without inflammation and without the use of postoperative steroids. BPC implants had a 100% retention rate at 8 weeks, when host stromal cells began to migrate into implants. Direct histochemical evidence of stromal tissue regeneration was observed by means of migrated host cells producing new collagen from within the implants. This study indicates that a cost-effective BPC extracellular matrix equivalent can incorporate cells passively to initiate regenerative healing of the corneal stroma, and is compatible with human stem or organ-specific cells for future therapeutic applications as a stromal replacement for treating blinding disorders of the cornea.

  • 237.
    Kozak Ljunggren, Monika
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences.
    Elizondo, Rodolfo A.
    Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
    Edin, Joel
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences.
    Olsen, David
    FibroGen Incorporated, San Francisco, CA, USA.
    Merrett, Kimberley
    Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences. Ottawa Hospital Research Institute–Vision Programme, Ottawa, Ontario, Canada.
    Lee, Chang-Jang
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences. Ottawa Hospital Research Institute–Vision Programme, Ottawa, Ontario, Canada.
    Salerud, Göran
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Polarek, James
    FibroGen Incorporated, San Francisco, CA, USA.
    Fagerholm, Per
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuroscience. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Ophthalmology in Linköping.
    Griffith, May
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences.
    Effect of Surgical Technique on Corneal Implant Performance2014In: Translational Vision Science & Technology, ISSN 2164-2591, Vol. 3, no 2, p. 1-13Article in journal (Refereed)
    Abstract [en]

    Purpose: Our aim was to determine the effect of a surgical technique on biomaterial implant performance, specifically graft retention.

     

    Methods: Twelve mini pigs were implanted with cell-free, 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS) cross-linked recombinant human collagen type III (RHCIII) hydrogels as substitutes for donor corneal allografts using overlying sutures with or without human amniotic membrane (HAM) versus interrupted sutures with HAM. The effects of the retention method were compared as well as the effects of collagen concentration (13.7% to 15% RHCIII).

    Results: All implanted corneas showed initial haze that cleared with time, resulting in corneas with optical clarity matching those of untreated controls. Biochemical analysis showed that by 12 months post operation, the initial RHCIII implants had been completely remodeled, as type I collagen, was the major collagenous protein detected, whereas no RHCIII could be detected. Histological analysis showed all implanted corneas exhibited regeneration of epithelial and stromal layers as well as nerves, along with touch sensitivity and tear production. Most neovascularization was seen in corneas stabilized by interrupted sutures.

    Conclusions: This showed that the surgical technique used does have a significant effect on the overall performance of corneal implants, overlying sutures caused less vascularization than interrupted sutures.

    Translational Relevance: Understanding the significance of the suturing technique can aid the selection of the most appropriate procedure when implanting artificial corneal substitutes. The same degree of regeneration, despite a higher collagen content indicates that future material development can progress toward stronger, more resistant implants.

  • 238. Kvernebo, K.
    et al.
    Salerud, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Evaluation of lower limb muscle blood flow by single fiber laser Doppler flowmetry1987In: 7th Nordic Meeting on Medical and Biological Engineering,1987, 1987, p. 41-Conference paper (Refereed)
  • 239. Kvernebo, K.
    et al.
    Salerud, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Kontinuerlig målning av muskelperfusjon med singel fiber laser Doppler flowmeter1987In: Norsk kirurgisk forening. Vetenskaplige förhandlinger,1987, 1987, p. 77-78Conference paper (Other academic)
  • 240. Kvernebo, K.
    et al.
    Salerud, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Single fiber laser Doppler flowmetry in the evaluation of lower limb muscle blood flow1987In: Nordisk Kirurgisk Förenings 43. Kongress,1987, 1987Conference paper (Other academic)
    Abstract [en]

      

  • 241. Kvernebo, K.
    et al.
    Salerud, Göran
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Single fibre laser Doppler flowmetry in the evaluation of human muscle blood flow1987In: Microcirculation - an update, vol 1 / [ed] Masaharu Tsuchiya, Amsterdam: Excerpta medica , 1987, p. 335-338Chapter in book (Other academic)
  • 242. Kvernebo, K.
    et al.
    Staxrud, L.E.
    Salerud, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Assessment of Human Muscle Blood Perfusion with Single-Fiber Laser Doppler Flowmetry.1990In: Microvascular Research, ISSN 0026-2862, E-ISSN 1095-9319, Vol. 39, p. 376-385Article in journal (Refereed)
  • 243.
    Kybartaite, Asta
    et al.
    University of Tampere, Finland.
    Salerud, Göran
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Malmivuo, Jakko
    University of Tampere, Finland.
    Developing practice of e-Learning application in Biomedical Engineering in Europé2010Conference paper (Refereed)
  • 244.
    Källman, Ulrika
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Nursing Science. Linköping University, Faculty of Medicine and Health Sciences. Södra Älvsborgs Sjukhus, Sweden.
    Bergstrand, Sara
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Ek, Anna-Christina
    Linköping University, Department of Medical and Health Sciences, Division of Nursing Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Local Health Care Services in Central Östergötland, Department of Emergency Medicine.
    Engström, Maria
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Lindgren, Margareta
    Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Department of Medical and Health Sciences, Division of Nursing Science.
    Blood flow responses over sacrum in nursing home residents during one hour bed rest2016In: Microcirculation, ISSN 1073-9688, E-ISSN 1549-8719, Vol. 23, no 7, p. 530-539Article in journal (Refereed)
    Abstract [en]

    ObjectivesTo describe individual BF responses in a nursing home resident population for one-hour periods of bed rest. MethodsBF was measured for one hour over the sacrum in 0 degrees supine position and 30 degrees supine tilt position in 25 individuals aged 65 y or older while lying on a pressure-redistributing mattress. Measurements were made at three tissue depths (1, 2, and 10 mm) using the noninvasive optical techniques, LDF and PPG. ResultsEleven participants had a PIV response at 1mm depth in both positions and seven participants had a lack of this response at this depth and positions. The BF response at 1mm depth appeared immediately and remained over, or below, baseline for the entire 60min of loading in both positions. These BF patterns were also seen in deeper tissue layers. ConclusionsThe cutaneous BF response among the nursing home residents was distinct, appeared early, and remained during the one hour of loading.

  • 245.
    Källman, Ulrika
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Nursing Science. Linköping University, Faculty of Health Sciences.
    Bergstrand, Sara
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Ek, Anna-Christina
    Linköping University, Department of Medical and Health Sciences, Division of Nursing Science. Linköping University, Faculty of Health Sciences. Region Östergötland, Local Health Care Services in Central Östergötland, Department of Emergency Medicine.
    Engström, Maria
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Lindgren, Margareta
    Linköping University, Department of Medical and Health Sciences, Division of Nursing Science. Linköping University, Faculty of Health Sciences.
    Nursing staff induced repositionings and immobile patients' spontaneous movements in nursing care.2016In: International Wound Journal, ISSN 1742-4801, E-ISSN 1742-481X, Vol. 13, no 6, p. 1168-1175Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to investigate nursing staff induced repositionings and the patients' spontaneous movements during the day and night among older immobile patients in nursing care. Furthermore, the aim was to identify factors associated with the nursing staff induced repositionings and the patients' spontaneous movement frequency. An observational cross-sectional design was used. Spontaneous movements among patients (n = 52) were registered continuously using the MovinSense monitoring system. The nursing staff documented each time they repositioned the patient. Patients spontaneous movements were compared with nursing staff induced repositionings. There were large variations in the patients' spontaneous repositioning frequency during both days and nights, which shows that, although immobilised, some patients frequently reposition themselves. Analgesics were positively related to the movement frequency and psycholeptics were negatively related. The nursing staff more often repositioned the patients who were assessed as high risk than those assessed as low risk, but the patients' spontaneous movement frequency was not correlated to the risk score. This may be important when planning repositioning schedules. A monitoring system may be useful in decision making with regard to planning repositioning and positions used in the prevention of pressure ulcers among elderly immobile patients.

  • 246.
    Källman, Ulrika
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Nursing Science. Linköping University, Faculty of Health Sciences.
    Bergstrand, Sara
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Ek, Anna-Christina
    Linköping University, Department of Medical and Health Sciences, Division of Nursing Science. Linköping University, Faculty of Health Sciences. Region Östergötland, Local Health Care Services in Central Östergötland, Department of Acute Health Care in Linköping.
    Engström, Maria
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Lindgren, Margareta
    Linköping University, Department of Medical and Health Sciences, Division of Nursing Science. Linköping University, Faculty of Health Sciences.
    Sacral pressure-induced blood flow responses at different tissue depths during one hour supine bedrest in nursing home residents2015Manuscript (preprint) (Other academic)
    Abstract [en]

    Background. Pressure induced vasodilation (PIV) protects the skin from pressure induced ischemia. PIV responses at individual level during a long-term measurement period have not previously been described in an elderly population in a clinically relevant situation.

    Aim. To describe individual PIV responses in a nursing home resident population for 1-hour periods of bed rest.

    Method. From May 2011 to August 2012, blood flow at three tissue depths was measured for one hour over the sacrum in 0° supine position and 30° supine tilt position in 25 individuals aged 65 years or older while lying on a pressure redistributing mattress. Measurements were made using the non-invasive optical techniques Laser Doppler Flowmetry (LDF) and photoplethysmography. The individuals were divided into a PIV group and a non-PIV group based upon the LDF data.

    Results. In the PIV group, the blood flow in almost all cases increased immediately and remained over baseline for the entire 60 minutes of loading in both positions, while the blood flow decreased immediately and remained below baseline in the non-PIV group. These blood flow patterns were also seen in deeper tissue layers although a PIV response was most common in the underlying tissue in both groups.

    Conclusion. The cutaneous blood flow response among the nursing home residents was distinct, appeared early and remained during the one hour of loading in both the PIV and non-PIV group. The non-PIV group may be more vulnerable to pressure and thus may be at risk for pressure ulcer development. More research is needed in order to verify the results.

  • 247.
    Larsson, Marcus
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Favilla, Riccardo
    Institute of Clinical Physiology, Council of National Research, Pisa, Italy.
    Strömberg, Tomas
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
    Assessment of advanced glycated end product accumulation in skin using auto fluorescence multispectral imaging2017In: Computers in Biology and Medicine, ISSN 0010-4825, E-ISSN 1879-0534, Vol. 85, p. 106-111Article in journal (Refereed)
    Abstract [en]

    Several studies have shown that advanced glycation end products (AGE) play a role in both the microvascular and macrovascular complications of diabetes and are closely linked to inflammation and atherosclerosis. AGEs accumulate in skin and can be detected using their auto fluorescence (AF).A significant correlation exists between AGE AF and the levels of AGEs as obtained from skin biopsies. A commercial device, the AGE Reader, has become available to assess skin AF for clinical purposes but, while displaying promising results, it is limited to single-point measurements performed in contact to skin tissue. Furthermore, in vivo imaging of AGE accumulation is virtually unexplored.We proposed a non-invasive, contact-less novel technique for quantifying fluorescent AGE deposits in skin tissue using a multispectral imaging camera setup (MSI) during ultraviolet (UV) exposure. Imaging involved applying a region-of-interest mask, avoiding specular reflections and a simple calibration. Results of a study conducted on 16 subjects with skin types ranging from fair to deeply pigmented skin, showed that AGE measured with MSI in forearm skin was significantly correlated with the AGE reference method (AGE Reader on forearm skin, R=0.68, p=0.005). AGE measured in facial skin was borderline significantly related to AGE Reader on forearm skin (R=0.47, p=0.078). These results support the use of the technique in devices for non-touch measurement of AGE content in either facial or forearm skin tissue over time.

  • 248.
    Larsson, Marcus
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Nilsson, Henrik
    Linköping University, Department of Biomedical Engineering.
    Strömberg, Tomas
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    In vivo determination of local skin optical properties and photon path length by use of spatially resolved diffuse reflectance with applications in laser Doppler flowmetry2003In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 42, no 7-8, p. 124-134Article in journal (Refereed)
    Abstract [en]

    Methods for local photon pathlength and optical properties estimation, based on measured and simulated diffuse reflectance within 2mm from the light source, are proposed and evaluated in vivo on Caucasian human skin. The accuracy of the methods was good (2-7%) for pathlength and reduced scattering but poor for absorption estimation. Reduced scattering and absorption were systematically lower in the fingertip than in the forearm skin (633 nm). A maximum intra-site and inter-individual variation of ~35% in the average photon pathlength was found. The methodology was applied in laser Doppler flowmetry (LDF), where pathlength normalization of the estimated perfusion removed the optical property dependency.

  • 249.
    Larsson, Marcus
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Steenbergen, Wiendelt
    University of Twente, Faculty of Applied Physics, Enschede, The Netherlands.
    Strömberg, Tomas
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Influence Of Optical Properties and Fiber separation on Laser Doppler Flowmetry2002In: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 7, no 2, p. 236-243Article in journal (Refereed)
    Abstract [en]

    Microcirculatory blood flow can be measured using a laser Doppler flowmetry (LDF) probe. However, the readings are affected by tissue optical properties (absorption and scattering coefficient; µa and µs) and probe geometry. In this study the influence of optical properties (µa∈[0.053, 0.23] mm-1; µs∈[14.7, 45.7] mm-1) on LDF perfusion and sampling depth were evaluated for different fiber separations. In-vitro measurements were made on a sophisticated tissue phantom with known optical properties, mimicking blood flow at different depths. Monte Carlo simulations were carried out to extend the geometry of the tissue phantom.

    A good correlation between measured and simulated data was found. The

    simulations showed that, for a fixed flow at a discrete depth, the influence of µs or µa on the LDF perfusion increased with increasing flow depth and decreased with increasing fiber separation. For a homogeneous flow distribution, however, the perfusion varied 40% due to the variations in optical properties, almost independent of fiber separation (0.23-1.61 mm). Therefore, the effect in real tissue is likely to vary due to the unknown heterogeneous blood flow distribution. Further, LDF sampling depth increased with decreasing µs or µa and increasing fiber separation. For a fiber separation of 0.46 mm, the e-1 sampling depth ranged from 0.21-0.39 mm.

  • 250.
    Larsson, Marcus
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Steenbergen, Wiendelt
    Faculty of Applied Physics University of Twente, Enschede, NL.
    Strömberg, Tomas
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Influence of tissue phantom optical properties and emitting - receiving fiber distance on Laser Doppler flowmetry2000In: Progress in Biomedical Optics and Imaging,2000, San José: SPIE , 2000, p. 56-63Conference paper (Refereed)
    Abstract [en]

    The influence of emitting - receiving fiber distance on the perfusion signal in laser Doppler flowmetry (LDF) for a range of optical properties has been studied. A custom made LDF probe with eight 230 μm fibers arranged in a row was used. Measurements were made on a tissue phantom with three different sets of optical properties (P={μs; μa} [mm-1]; P1={14.7; 0.212}, P2={44.9; 0.226} and P3=(45.6; 0.0532}). A single moving disc simulated flow at four different depths. The noise-corrected perfusion for a given set of optical properties (P), fiber distance (l) and disc depth (d) is defined as Perf(ν,P,d,l)=k(P,d,l) v, where v is the speed of the rotating disc. The relative difference between two slopes, Δk(Pa,Pb,l,d), indicates how sensitive the LDF readings are to changes in optical properties (Pb → Pa) for given disc depth and fiber distance. Evaluation of Δk(P1,P2,d,l) (reflects changes in scattering coefficient, μs) and Δk(P3,P2,d,l) (reflects changes in absorption coefficient, μa) indicated that LDF perfusion was more sensitive to the changes in μs than in μa. The sensitivity also increased with increasing disc depth. A fiber distance of 920 [μm] was found to minimize these effects. E.g. the sensitivity due to the variations in μs, for fiber distance l1=920, l2=230 [μm] and for all disc depths, was Δk(P1,P2,l1)=[0.76, 1.06, 1.58, 2.40] and Δk(P1,P2,l2)=[1.61, 2.98, 5.04, 7.67].

2345678 201 - 250 of 565
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