Photon Propagation Correction in 3D Photoacoustic Image Reconstruction using Monte Carlo Simulation

Purpose: The purpose of this study is to develop a new 3-D iterative Monte Carlo algorithm to recover the heterogeneous distribution of molecular absorbers with a solid tumor. Introduction: Spectroscopic imaging (PCT-S) has the potential to identify a molecular species and quantify its concentration with high spatial fidelity. To accomplish this task, tissue attenuation losses during photon propagation in heterogeneous 3D objects is necessary. An iterative recovery algorithm has been developed to extract 3D heterogeneous parametric maps of absorption coefficients implementing a MC algorithm based on a single source photoacoustic scanner and to determine the influence of the reduced scattering coefficient on the uncertainty of recovered absorption coefficient. Material and Methods: This algorithm is tested for spheres and ellipsoids embedded in simulated mouse torso with optical absorption values ranging from 0.01-0.5/cm, for the same objects where the optical scattering is unknown (mu(s)'=7-13/cm), and for a heterogeneous distribution of absorbers. Results: Systemic and statistical errors in ma with a priori knowledge of mu(s)' and g are <2% (sphere) and <4% (ellipsoid) for all ma and without a priori knowledge of mu(s)' is <3% and <6%. For heterogenenous distributions of ma, errors are <4% and <5.5% for each object with a prior knowledge of mu s' and g, and to 7 and 14% when mu(s)' varied from 7-13/cm. Conclusions: A Monte Carlo code has been successfully developed and used to correct for photon propagation effects in simulated objects consistent with tumors.