Browsing by Author "Kara, Ercan."

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    Design of a dynamic optical property monitoring system: Studying the effect of temperature change
    (Thesis (Ph.D.)-Bogazici University. Institute of Biomedical Engineering, 2018., 2018.) Kara, Ercan.; Gülsoy, Murat,; Çilesiz, İnci.
    In laser applications, it is necessary to know the tissue optical properties before the treatment and how they change during the treatment. The optical monitoring system with double-integrating-sphere having a special sample heating apparatus was designed to investigate the e ect of temperature on optical properties. Temperature dependent optical property changes was investigated using lipid emulsion. It was found that the re ectance value showed negative correlation with temperature and transmittance showed positive correlation. Also, it was observed that the reduced scattering coe cient obtained using an inverse adding-doubling method showed a negative correlation with temperature, but there was no statistically signi cant change in absorption coe cient. The e ect of such optical property changes on the light propagation was displayed by Monte Carlo simulation. As a result, optical properties can change with temperature and this change must be taken into account for safer laser applications.|Keywords : Double-Integrating-Sphere, Temperature Effect, Optical Property, Monte Carlo Simulation.
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    Subband filtering of fNIRS data from schizophrenic subjects
    (Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2008., 2008.) Kara, Ercan.; Akın, Ata.
    Schizophrenia is a neurological disorder and typically persists for a life. Investigation of the cerebral hemodynamics of schizophrenic patients with a rapid, non-invasive and precise technique is required to improve the prognosis and guide therapeutic interventions. Functional Near-Infrared Spectroscopy (fNIRS) is a non-invasive brain imaging technique measuring the changes in oxy-hemoglobin and deoxy-hemoglobin particularly in prefrontal cortex. In this study, fNIRS was used during a Stroop task to investigate the differences in oscillatory dynamics between schizophrenic patients and control subjects. Spectral analysis and dyadic wavelet transform were employed to quantify the degree of loss of cerebral activation and to localize the major areas of loss of activation in the prefrontal cortex. In this study, it was found that specific brain areas are responsible for generating specific oscillatory patterns and energies of these patterns are significantly reduced in schizophrenic patients.|Keywords: Schizophrenia, Functional Near Infrared Spectroscopy (fNIRS), Spectral Analysis, Wavelet Decomposition, Stroop Task.