Study on polarization distribution characteristics of polarized light in scattering media

Cerebral blood flow (CBF) is the main basis for clinical diagnosis of cerebrovascular diseases such as cerebral infarction and cerebral hemorrhage. The local cerebral blood flow (rCBF) detection method based on optical heterodyne detection (OHD) is expected to achieve high-precision detection of rCBF. The purpose of this study is to study the polarization state distribution characteristics of polarized light in the scattering medium by Monte Carlo simulation method, and to guide the optimization of measurement position and source-detector separation when OHD method is used to detect rCBF, and improve the measurement sensitivity. The Monte Carlo simulation result shows that the proportion of photons maintaining polarization state in the weak scattering medium is greater than in the strong scattering medium, and the proportion of photons maintaining polarization state is inversely proportional to the source-detector separation. Among them, The photon ratio that maintains the polarization state is best when the scattering angle is 0 or pi. This study is of great significance for optimizing the source-detector separation and improving the sensitivity of OHD method for detecting rCBF.