Imaged backscatter from three-dimensional tissue structure

摘要

Abstract: When imaging the backscattered light from turbid tissue using a broadband illumination source, the random scattering of photons within the tissue causes wavelength-dependent optical coupling between pixels. That is, a photon may exit the tissue surface an extended distance away from its entry point. The resulting spectral crosstalk in the detected image can be explained by studying the mean photon path lengths through the tissue. Considering complex tissue geometries with features such as cylindrical vessels, these photons not only travel multiple paths due to wavelength- dependent absorption and scattering, but may also travel through multiple chromophores. To study the effects of 3D features in object space on backscattered light into the image plane, we have constructed a Monte Carlo simulation capable of modeling 3D photon propagation for a tissue slab with an embedded cylinder. The results of hemoglobin-bearing vessels as a primary chromophore are investigated. Because of the relationship between mean photon path length and photon exit angle, we have shown that the choice of entrance pupil in the imaging system plays an important role on the detected backscatter for the specific case of embedded cylinders.!21