(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: To determine the effect of tissue optical properties on the Cherenkov emission, and to investigate the influence of oblique incidence electron beams to the angular distribution of Cherenkov emission from tissue surface.
Methods: We use Monte Carlo modeling to simulate the generation of Cherenkov light upon different incidence electron beam angles and the its propagation in tissue. We simulate the spectrum of Cherenkov emission from 400-1000nm for a range of clinically relevant tissue optical properties. The absorption coefficient at each wavelength was determined based on the molar extinction coefficient spectra of oxy- and deoxyhaemoglobin with tissue oxygen saturation of 70%. The reduced scattering coefficient at each wavelength was approximated based on Mie theory. A semi-infinite geometry with uniform optical properties, anisotropy factor of 0.9 and a refractive mismatch of 1.4, was used in the simulations. Cherenkov photons are generated uniformly along a cone parallel to the central axis, with a cone angle of 43.5° which corresponds to 3MeV electron beam energy. The incident electron beam angle was increased from 0° (normal to tissue surface) to 20° at step of 5° to evaluate the effect of obliquely incident beams on the angular distribution of Cherenkov emission from tissue.
Results: Simulation results show that the intensity of Cherenkov emission decreases with tissue absorption and increases with tissue scattering. Tissue optical properties dependence of Cherenkov emission can be expressed in one dimensional function of diffuse reflectance(Rd). Cherenkov light emitted from tissue surface follows the Lambertian distribution for electron beam incident perpendicularly to the tissue surface.
Conclusion: Tissue optical properties dependence of Cherenkov emission can be expressed using equation y=0.117exp(4.88Rd). Cherenkov emission from tissue surface due to normally incident electron beam has no angular dependence. The angular distribution of Cherenkov emission due to obliquely incident electron beam will be examined.
Keywords
Not Applicable / None Entered.
Taxonomy
TH- External beam- electrons: Monte Carlo dosimetry
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