Light transport in trabecular bone:: Monte Carlo simulation based on 3D triangle meshes

Light transport in trabecular bone is not well understood despite its clinical interest. Recent experimental studies on optical bone biopsy are lacking models that relate their measurements to the underlying morphology and thus to tissue condition. Laser surgery can also benefit from a better understanding of energy distribution in cancellous bone. A Monte Carlo (MC) simulation environment, able to efficiently compute complex geometries and account for refraction and reflection on tissue boundaries has been developed to provide the missing insight. The geometry description is based on a 3D triangle mesh organised in a bounding-volume hierarchy. This efficient structure allows a fast photon-surface intersection test, ensuring a sufficient number of photon paths and thus a good signal-to-noise ratio. The simulation program has been validated against well-known problems of refractive optics and turbid media. This new tool has been applied to a set of numerical phantoms indicating that morphology may have a fundamental impact on long-range light transport. The simulation environment has also been used on high-resolution models of trabecular bone, based on micro-CT scans. Calculation of time resolved signals in transmission and reflectance geometries has been demonstrated, paving the way to numerical evaluation of new minimally invasive diagnostic techniques, and offering a link to evaluation of Optical Coherence Tomography (OCT) in complex heterogeneous geometries. Preliminary experimental results in support of the mentioned effects are presented.