Optical properties of native and coagulated lamb brain tissues in vitro in the visible and near-infrared spectral range

Abstract

The aim of this study was to estimate optical properties ofnative and coagulated lamb brain tissues at three different temperatures (45⁰C, 60⁰C, 80⁰C) by means of measured data which formed due to light-tissue interactions in visible and near-infrared spectral range in vitro. For dosimetry planning and accurate surgery,information about optical properties of brain tissue is required. Since optical properties ofbrain tissue may change due to thermal effects during laser therapy, knowledge of opticalproperties of brain tissue coagulated at different temperatures should also be known for surgery. During this experimental study, optical properties of cerebellum, brainstem, cortical (grey matter), and sub-cortical regions (white matter) of frontal lobe tissues oflamb brain were estimated. For estimation, optical measurement data were determined foreither native or coagulated tissues. These measurement data were diffused transmittance,diffused reflectance, total reflectance and total transmittance.In order to measure these data, an optical system was designed; light coming froma light source was focused on the monochromator which can emit light at desired singlewavelength. Incoming light from exit slit of monochromator was focused on integratingsphere by means of optic lenses in order to get measured data from lock-in amplifier. Afterwards, data obtained from experiments were used to estimate optical properties oftissues by means of a software (CAL-g3) written in Biophotonics Laboratory of Boğazici University. As a conclusion, it was stated that both and values of tissues increased astemperature increases. Also scattering coefficients decreased with the wavelength for alltissue types due to increase in Mie scattering.|Keywords: Monochromator, tissue characterization, light-tissue interaction.