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  • 2201.
    Öberg, Åke
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Sundqvist, Tommy
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för molekylär och klinisk medicin, Medicinsk mikrobiologi.
    Johansson, Anders
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Assessment of cartilage thickness utilising reflectance spectroscopy2004Inngår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 42, nr 1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new principle for cartilage layer thickness assessments in joints is presented. It is based on the differences between the absorption spectra of cartilage and subchondral bone (containing blood). High-resolution ultrasound measurements of cartilage thickness were compared with reflection spectroscopy data from the same area of bovine hip joint condyles. A simple mathematical model allowed calculation of thickness and comparison with ultrasound data. The cartilage thickness was changed by being ground in short episodes. For thicker cartilage layers, a high degree of reflection in the 400-600nm wavelength interval was seen. For thinner cartilage layers, the characteristics of the spectra of blood and bone dominated those of cartilage. The mean (±SD) thickness of intact cartilage was 1.21± 0.30 mm (n = 30). In an exponential regression model, spectroscopic estimation of cartilage thickness showed a correlation coefficient of r= 0.69 (n = 182). For thinner cartilage layers (d<0.5mm), the mean model error was 0.19±0.17mm. Results from a bi-layer Monte Carlo simulation supported the assumption of an exponential relationship between spectroscopy data and reference ultrasound data. The conclusion is that optical reflection spectroscopy can be used for cartilage layer thickness assessment.

  • 2202.
    Öberg, Åke
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Sundqvist, Tommy
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för molekylär och klinisk medicin, Medicinsk mikrobiologi.
    Johansson, Anders
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Sundberg, Mikael
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Characterisation of the cartilage/bone interface utilising reflectance spectroscopy2001Inngår i: 23rd Annual International Conference IEEE EMBS,2001, IEEE , 2001, Vol. 3, s. 3002-3004Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Optical reflection spectra of the cartilage/bone interface from hip joints of cows were studied. When comparing to ultrasonic measurement, it was found that cartilage thickness could be extracted using optical reflectance spectroscopy. For thicker cartilage layers, a high reflection for the wavelengths 400-600 nm was seen, and for thinner cartilage layers, the characteristic spectra of blood and bone dominated. The optical reflectance spectra may be used to characterise cartilage, and specifically cartilage thickness, in connection with in situ diagnosis or autologous chondrocyte implantation (ACI).

  • 2203.
    Öberg, Åke
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Tamura, T.
    Lindberg, Lars-Göran
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Salerud, Göran
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    A comparison between laser Doppler flowmetry and photoplethysmography1988Inngår i: Betch. AMH CCCP,1988, 1988, s. 82-Konferansepaper (Fagfellevurdert)
  • 2204.
    Ödman, Svante
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    On biomedical electrode technology: with special reference to long-term properties and movement-induced noise in surface electrodes1980Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The aim of the present investigation was to improve the quality of surface electrode measurements. Long-term properties of commercially available ECG-electrodes were studied by investigating polarization potentials, electrode impedance, adhesion and skin reactions during a period of 7 days. The most stable polarization potentials were obtained for Ag/AgC1-electrodes and stable electrode impedance were obtained for disposable electrodes with stable adhesion and equipped with an electrode capsule. Unchanged adhesion and mechanical strength were shown by disposable electrodes with large self-adhesive collars.

    Movement-induced potentials of streaming potential type were studied in various electrode configurations. The geometric design of the electrode was important for reduction of noise generated by the movement of gel. Potential and impedance variations were measured for electrode movements in electrolytes relative to the skin. The impedance variations were small and streaming potentials with a magnitude of up to 10μV were recorded. The deformation potentials generated in the skin dominate the disturbance pattern in surface electrode recordings. Potential and impedance variations studied with varying mechanical stress upon skin showed that the impedance variations did not bring about the potential variations. The size of potential variations in skin and related mechanical stress possess a non-linear relationship which varies between individuals. A non-linear character of the time sequence of stretch potentials was found.

    The spread of deformation potentials was studied in the skin area around and beneath surface electrodes. When stretching a rectangular skin zone between two plates fixed to the skin the highest potentials were obtained in the zone. The magnitude of the potentials decreased with the distance to the zone. Stretch potentials could be reduced but not geometrically limited by fixing the skin to a rigid electrode collar. The potential spread is a consequence of successively decreasing deformation.

  • 2205. Ödman, Svante
    et al.
    Levitan, Herbert
    Robinson, Peter J
    Michel, Mary Ellen
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Rapoport, Santley I
    Peripheral nerve as an osmometer: role of endoneurial capillaries in frog sciatic nerve.1987Inngår i: American Journal of Physiology, ISSN 0002-9513, E-ISSN 2163-5773, Vol. 252, nr 3 Pt 1, s. C335-41Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The sciatic nerve of the frog was perfused in vivo with isotonic Ringer solution followed by Ringer made hypertonic by addition of sucrose or of NaCl. Nerve diameter and endoneurial hydrostatic pressure fell during hypertonic Ringer perfusion. Using a model that describes the elastic and osmotic properties of the nerve, sigma sLp, the product of the osmotic reflection coefficient at endoneurial capillaries for s equals sucrose or NaCl (which approximates 1), and of capillary hydraulic conductivity, was found to equal 73 X 10(-13) cm3 X s-1 X dyn-1. The nerve is elastic. It has a compliance K of 3.7 X 10(-5) cm2 X mmHg-1, corresponding to a modulus of elasticity E of the perineurium equal to 1.2 X 10(6) dyn X cm-2. The results indicate that the nerve behaves as an osmometer during vascular perfusion, due to the low permeability of endoneurial capillaries to small solutes such as NaCl and sucrose. A low capillary hydraulic conductivity limits bulk water flow between blood and nerve, and a low compliance limits nerve swelling and edema.

  • 2206.
    Öhman, Fredrik
    Linköpings universitet, Institutionen för medicinsk teknik.
    Går det att mäta blodtryck med fotopletysmografi och bioakustisk sensor i kombination?2004Independent thesis Basic level (professional degree)Oppgave
    Abstract [sv]

    The aim of the work was to investigate the possibility to combine information from PPG and bio-acoustic technology to extract information that is related to the blood pressure. The measurements have been carried out with several different configurations. First the relation between arterial sounds and the PPG-signal was studied. After those measurements with both PPG and the bio- acoustic technique was concluded on people in different positions and after riding a bike. The goal was to vary the blood pressure. The conclusion that can be drawn in this report is that the bio-acoustic and the PPG-signal in peripheral arteries have the same source. That implies that arterial sounds are a product of turbulence when the pulse wave passes by. Further it can be assumed that it is the first heart sound that is represented in the arterial sounds. The time before and after the arterial sound in one heart cycle vary whit the blood pressure. There relationship seems also to vary with the bloodpressure but it vary differently under different conditions.

  • 2207.
    Özarslan, Evren
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Yolcu, Cem
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Herberthson, Magnus
    Linköpings universitet, Matematiska institutionen, Matematik och tillämpad matematik. Linköpings universitet, Tekniska fakulteten.
    Knutsson, Hans
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Westin, Carl-Fredrik
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten. Laboratory for Mathematics in Imaging, Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA.
    Influence of the Size and Curvedness of Neural Projections on the Orientationally Averaged Diffusion MR Signal2018Inngår i: Frontiers in Physics, E-ISSN 2296-424X, Vol. 6, s. 1-10, artikkel-id 17Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Neuronal and glial projections can be envisioned to be tubes of infinitesimal diameter as far as diffusion magnetic resonance (MR) measurements via clinical scanners are concerned. Recent experimental studies indicate that the decay of the orientationally-averaged signal in white-matter may be characterized by the power-law, Ē(q) ∝ q−1, where q is the wavenumber determined by the parameters of the pulsed field gradient measurements. One particular study by McKinnon et al. [1] reports a distinctively faster decay in gray-matter. Here, we assess the role of the size and curvature of the neurites and glial arborizations in these experimental findings. To this end, we studied the signal decay for diffusion along general curves at all three temporal regimes of the traditional pulsed field gradient measurements. We show that for curvy projections, employment of longer pulse durations leads to a disappearance of the q−1 decay, while such decay is robust when narrow gradient pulses are used. Thus, in clinical acquisitions, the lack of such a decay for a fibrous specimen can be seen as indicative of fibers that are curved. We note that the above discussion is valid for an intermediate range of q-values as the true asymptotic behavior of the signal decay is Ē(q) ∝ q−4 for narrow pulses (through Debye-Porod law) or steeper for longer pulses. This study is expected to provide insights for interpreting the diffusion-weighted images of the central nervous system and aid in the design of acquisition strategies.

  • 2208.
    Özarslan, Evren
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Yolcu, Cem
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Herberthson, Magnus
    Linköpings universitet, Matematiska institutionen, Matematik och tillämpad matematik. Linköpings universitet, Tekniska fakulteten.
    Westin, Carl-Fredrik
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten. Laboratory for Mathematics in Imaging, Department of Radiology, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States.
    Knutsson, Hans
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Effective Potential for Magnetic Resonance Measurements of Restricted Diffusion2017Inngår i: Frontiers in Physics, E-ISSN 2296-424X, Vol. 5, artikkel-id 68Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The signature of diffusive motion on the NMR signal has been exploited to characterize the mesoscopic structure of specimens in numerous applications. For compartmentalized specimens comprising isolated subdomains, a representation of individual pores is necessary for describing restricted diffusion within them. When gradient waveforms with long pulse durations are employed, a quadratic potential profile is identified as an effective energy landscape for restricted diffusion. The dependence of the stochastic effective force on the center-of-mass position is indeed found to be approximately linear (Hookean) for restricted diffusion even when the walls are sticky. We outline the theoretical basis and practical advantages of our picture involving effective potentials.

42434445 2201 - 2208 of 2208
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