ECE532 Biomedical Optics|
Steven L. Jacques, Scott A. Prahl
Oregon Graduate Institute
Time-resolved Monte Carlo:
The output file "trmc.out" is plotted below to illustrate the output of the "trmc.c" program. The data for four timepoints are shown as solid circles: 0.050, 0.100, 0.500, and 1.000 ns. Also shown as solid lines are the predictions of diffusion theory.
Note that the original impulse traveling at the speed of light will have reached 1.12 cm at 0.050 ns, for which the Monte Carlo result shows negligible photon density beyond 1 cm and no photon density at depths greater than 1.12 cm. But diffusion theory predicts that some photon density has reached depths deeper than 1.12 cm at 0.050 ns. Clearly, this is not possible. Diffusion theory overpredicts the penetration of the leading edge of the photon density, i.e., the deep region near the depth reached by the survival portion of the original impulse traveling at the speed of light.