18 January 2005 Relationship between backscattered photon numbers and their scattering events in a turbid media
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Various optical imaging techniques had been brought out and studied for imaging in turbid media such as bio-tissues. However, there’re always limitations or problems here and there. Among them many are related to light scattering in the media. In this paper we provide a new insight into these questions and tried to give some possible explanations. The distribution of backscattered photon numbers on scattering events of light was studied for what is to our knowledge the first time. A Monte Carlo (MC) method was used to calculate how many photons will reemit from media as their scattering events increase. Various illuminant conditions and detecting methods were simulated, results show that instead of easily took feint that photons reemitted from tissue increases/decreases as scattering events accumulates; backscattered photon numbers increase firstly and decrease later. The peak position, peak value and exact curve shape depend on illuminant conditions, monitoring method and tissue optical parameters. From these curves two basic conclusions could be drawn as follows: (1) the chance of single scattering photon packet exiting the tissue exists, but decreases dramatically as internal source moves deep into media. This suggests that theoretically many coherent imaging approaches are feasible, but good imaging depth requires high power density, this leads to difficulty in improving imaging depth. (2) as for the majority of backscattered photons, the number of average scattering events has a close relationship with mean free path -- one of the most important tissue optical parameters. Our simulation results will lead to several interesting explanations to many present problems.
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Lanqing Xu, Hui Li, Yongping Zheng, Shusen Xie, "Relationship between backscattered photon numbers and their scattering events in a turbid media", Proc. SPIE 5630, Optics in Health Care and Biomedical Optics: Diagnostics and Treatment II, (18 January 2005); doi: 10.1117/12.576902; https://doi.org/10.1117/12.576902

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