Improved importance sampling for Monte Carlo simulation of time-domain optical coherence tomography

Abstract

Abstract:We developed an importance sampling based method that significantly speeds up the calculation of the diffusive reflectance due to ballistic and to quasi-ballistic components of photons scattered in turbid media: Class I diffusive reflectance. These components of scattered photons make up the signal in optical coherence tomography (OCT) imaging. We show that the use of this method reduces the computation time of this diffusive reflectance in time-domain OCT by up to three orders of magnitude when compared with standard Monte Carlo simulation. Our method does not produce a systematic bias in the statistical result that is typically observed in existing methods to speed up Monte Carlo simulations of light transport in tissue. This fast Monte Carlo calculation of the Class I diffusive reflectance can be used as a tool to further study the physical process governing OCT signals, e.g., obtain the statistics of the depth-scan, including the effects of multiple scattering of light, in OCT. This is an important prerequisite to future research to increase penetration depth and to improve image extraction in OCT. Med. Phys. 10(6), 824-830 (1983). 9. L. Wang, S. L. Jacques, and L. Zheng, "MCML--Monte Carlo modeling of light transport in multi-layered tissues," Comput. Methods Programs Biomed. 47(2), 131-146 (1995). 10. N. G. Chen and J. Bai, "Estimation of quasi-straightforward propagating light in tissues," Phys. Med. Biol. 44(7), 1669-1676 (1999). 11. N. Chen, "Controlled Monte Carlo method for light propagation in tissue of semi-infinite geometry," Appl. Opt.46(10), 1597-1603 (2007

Almost instantaneous Monte Carlo calculation of optical coherence tomography signal using graphic processing unit

“…The introduced statistical bias is eliminated by reducing the weight of the photon packet by a likelihood ratio. Further details of the method can be found in [2,3]. This IS algorithm has been implemented using CUDA (Compute Unified Device Architecture) to take advantage of a massively multi-threaded NVIDIA GPU hardware, which allows the simulation of several hundreds of photon packets in parallel.…”

“…Different methods have been used to speed up MC simulations, including but not limited to variance reduction techniques and parallel computation methods. An importance sampling (IS) technique that achieved a computational speed up of three orders of magnitude over a standard MC approach was shown in [2,3]. Parallel computation on Graphics Processing Units (GPUs) and GPU clusters have recently been demonstrated to speed up MC calculations in light transport models of multi-layered tissues by two to three orders of magnitude [4].…”

Monte Carlo simulation of optical coherence tomography for turbid media with arbitrary spatial distributions

“…Earlier, we developed fast Monte Carlo methods to compute OCT signals from a turbid multilayered object. 7,8 In this article, we generalize our previous work to include objects with arbitrary spatial distributions.…”

“…Many available OCT simulators [7][8][9][10][11][12] are based on the Monte Carlo simulation of light transport in multilayered turbid media (MCML) that was developed by Wang et al 13 MCML is still a popular simulator. However, its main drawback is its restriction to multilayered media.…”

Fast calculation of multipath diffusive reflectance in optical coherence tomography

“…In [4], we reviewed previous methods proposed to speed up Monte Carlo simulations and we showed how one can extend the method in [3] using importance sampling to significantly speed up the calculation of the OCT signal from the entire depth range imaged that results from the ballistic and the quasi-ballistic scattered photons, the Class I reflectance, without significant residual bias in the statistical result. That importance sampling method consists of applying multiple biases towards the source after the first biased scattering is applied to the photon packets, and using a photon splitting procedure.…”