Time Resolved Photon Fluencies for Different Input Angle Sources

Abstract The variation of photon fluence distributions [photon/cm2.s] for different input angle laser sources was shown by researchers experimentally [1]. According to this philosophy, different input angle source and detector photon entrance from tissue surface into imaging media have different photon fluence distributions for a specific tissue type. In this study, different input angle simulations were used for pulsed laser photons which uses time resolved (TR) Monte Carlo (MC) photon-tissue interaction simulation program to prove the philosophy in TR run mode. TR run mode MC simulation program trmc.c [2] was modified and used to generate TR photon counts inside the homogenous simulation environment. It has homogeneous tissue optical properties, absorption μa = 0.1 cm-1, scattering μs = 100 cm-1, and anisotropy g = 0.90 coefficients. Multi-input angle philosophy was first demonstrated by the researchers [1]. It was defined and experimentally proven. Photon fluencies which are forward model weight matrix coefficients differences were successfully shown for TR laser as a general procedure. In this study, differences were drawn for seven different input angle sources with pulsed laser photons. The proof-of-concept philosophy was shown successfully. The purpose of the use of pulsed laser is to show the righteousness of the philosophy in TR run mode, since the TR diffuse optical tomography (TRDOT) device would be made as a biomedical optic imaging (BOI) device. Cylindrical radial coordinate system which was defined in trmc.c [2] in earlier was used, the code was modified, and photon fluencies were generated based on the different input angle laser photons. Cylindrical coordinate system has 1 cm and 36-element radial r, and depth z grids. 100.000 photons were sent from pencil beam tissue surface point. Photons would be thought as group of ultra-narrow band pulsed laser photons. The main purpose of showing photon fluencies for different laser source input angles were succeeded and image reconstruction procedure was also applied. Ten time series were used which are [4, 8, 12, 16, 22, 26, 30, 38, 46, 52] picoseconds (ps). Different input angle photon fluence distribution figures were drawn. These are 0º, 15º, 30º, 45º, 60º, 75º, 90º. Photon fluence differences were also drawn and observed for different input angle laser sources. Forward model problem different input angle laser source and detector transfer functions were also drawn. Finally inlusion was embedded inside the homogenous simulation environment and images were reconstructed for both scenarios and localization error (LE), and concentration error (CE) was calculated for both scenarions and compared with each other.