Light transport modeling in highly complex tissues using implicit mesh-based Monte Carlo algorithm

Abstract

The mesh-based Monte Carlo (MMC) technique has grown tremendously since its initial publication nearly a decade ago. It is now recognized as one of the most accurate Monte Carlo (MC) methods, providing accurate reference solutions for the development of novel biophotonics techniques. In this work, we aim to further advance MMC to address a major challenge in biophotonics modeling, i.e. light transport within highly complex tissues, such as dense microvascular networks, porous media and multi-scale tissue structures. Although the current MMC framework is capable of simulating light propagation in such media given its generality, the run-time and memory usage grow rapidly with increasing media complexity and size. This greatly limits our capability to explore complex and multi-scale tissue structures. Here, we propose a highly efficient implicit mesh-based Monte Carlo (iMMC) method that incorporates both mesh- and shape-based tissue representations to create highly complex yet memory efficient light transport simulations. We demonstrate that iMMC is capable of providing accurate solutions for dense vessel networks and porous tissues while reducing memory usage by greater than a hundred- or even thousand-fold. In a sample network of microvasculature, the reduced shape complexity results in nearly 3x speed acceleration. The proposed algorithm is now available in our open-source MMC software at http://mcx.space/#mmc.

BlenderPhotonics – an integrated open-source software environment for 3-D meshing and photon simulations in complex tissues

“…In the first example, we use the rough-surface creation feature in Blender and investigate how changing the roughness of a skin-mimicking surface could lead to different light distributions and results. In the second example, we can combine BlenderPhotonics with one of our most recent advances in MC simulation – the implicit MMC (iMMC) algorithm 27 – to potentially enable the study of the impact of human hairs in fNIRS measurements. To the best of our knowledge, these types of studies have not been reported by other MC simulators.…”

“…A special script is used to export all hair vertices and the head mesh into a file that is processed by the Iso2Mesh toolbox to create iMMC simulation models for subsequent light transport simulations. 27…”

“…For example, wide-field MMC was added by Yao et al in 2016, 26 which is particularly important for supporting the active development of spatial frequency domain imaging (SFDI) techniques in recent years. In addition, implicit mesh-based Monte Carlo algorithm (iMMC), proposed by Yuan et al, 27 combines shape-based modeling and mesh-based anatomical models to enable simulations of extremely complex tissue structures such as dense vessel networks.…”

Meshless Monte Carlo Radiation Transfer Method for Curved Geometries using Signed Distance Functions

“…The lack of these accurate reflections meant a massive decrease in the accuracy of the simulation of the light distribution in the bottle, as the bottle acts as a cylindrical lens on the light, see SI 8. The vessels are a 3D synthetic microvascular network from data published in [45] and preprocessed by Yuan et al [46]. We model the slab of tissue using a box SDF (second shape in bottom left panel of Figure 1), and the vessels as a collection of capsule SDFs (third shape in top left panel of Figure 1) which are then joined together using the CSG operator union (bottom left operation in top right panel of Figure 1).…”

MCX Cloud – a modern, scalable, high-performance and in-browser Monte Carlo simulation platform with cloud computing

“…8 More recently, hybrid approaches that combine shape representations offer further computational efficiency and accuracy. [12][13][14][15] These hybrid approaches include 1) dual-grid MMC (DMMC) 12 that combines a coarse tetrahedral mesh with a dense voxelated output volume, 2) splitvoxel MC (SVMC) 14 that combines curved surface meshes within a compact voxel data structure, and 3) implicit MMC (iMMC) 15 that combines a skeletal tetrahedral mesh with implicitly defined shapes such as tubes, spheres and thin membranes. These enhancements in modeling geometry have resulted in significantly improved accuracy, which can be directly translated to further speed enhancement while achieving the same output accuracy as conventional approaches.…”