Monte Carlo Photon Transport

tMCimg uses a Monte Carlo algorithm to model the transport of photons through 3D highly volumes with spatially varying optical properties and arbitrary boundary conditions. Both highly-scattering tissues (e.g. white matter) and weakly scattering tissues (e.g. cerebral spinal fluid) are supported. Using the clinical structural information provided by MRI, X-Ray CT, or ultrasound, accurate solutions to the photon migration forward problem are found in times ranging from minutes to hours, depending on the optical properties and the computing resources available.

Program Executables and Source Code

Program Documentation

tMCimg models the propagation of photons through the medium using a Monte Carlo algorithm. For each photon an initial position and orientation is specified in the input file. Assuming no boundaries are encountered along the way, the photon advances one scattering length (selected at random from an exponential distribution of possible lengths characterized by the scattering coefficient \mu_s). After traveling a full scattering length, the photon is first attenuated and then it scatters into a new direction determined by a Heyney-Greenstein distribution and the optical properties of the medium. The process is then iterated until the photon either leaves the system or a user configurable time-gate expires. By sampling many possible paths an estimate of the overall photon distribution is built up (which is asymptotically exact as the number of photons sampled increases). This information is saved to disk for future use.

Proper documentation is still being written. For now, the source code is your best guide.

Sample Files

The following are the input and segmentation files used to generate Figures 1 and 2 of figures in our most recent Optics Express paper.