FullMonte: a framework for high-performance Monte Carlo simulation of light through turbid media with complex geometry

Emerging clinical applications including bioluminescence imaging require fast and accurate modelling of light propagation through turbid media with complex geometries. Monte Carlo simulations are widely recognized as the standard for high-quality modelling of light propagation in turbid media, albeit with high computational requirements. We present FullMonte: a flexible, extensible software framework for Monte Carlo modelling of light transport from extended sources through general 3D turbid media including anisotropic scattering and refractive index changes. The problem geometry is expressed using a tetrahedral mesh, giving accurate surface normals and avoiding artifacts introduced by voxel approaches. The software uses multithreading, Intel SSE vector instructions, and optimized data structures. It incorporates novel hardware-friendly performance optimizations that are also useful for software implementations. Results and performance are compared against existing implementations. We present a discussion of current state-of-the-art algorithms and accelerated implementations of the modelling problem. A new parameter permitting accuracy-performance tradeoffs is also shown which has significant implications including performance gains of over 25% for real applications. The advantages and limitations of both CPU and GPU implementations are discussed, with observations important to future advances. We also point the way towards custom hardware implementations with potentially large gains in performance and energy efficiency.