Forced Detection Monte Carlo Algorithms for Accelerated Blood Vessel Image Simulations

Abstract

Two forced detection (FD) variance reduction Monte Carlo algorithms for image simulations of tissue‐embedded objects with matched refractive index are presented. The principle of the algorithms is to force a fraction of the photon weight to the detector at each and every scattering event. The fractional weight is given by the probability for the photon to reach the detector without further interactions. Two imaging setups are applied to a tissue model including blood vessels, where the FD algorithms produce identical results as traditional brute force simulations, while being accelerated with two orders of magnitude. Extending the methods to include refraction mismatches is discussed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Measurement depth and volume in laser Doppler flowmetry

“…Previous studies have demonstrated a high correlation between Monte Carlo based simulations and LDF measurements (de Mul, Koelink et al 1995;Kienle, Patterson et al 1996;Larsson, Steenbergen et al 2002;Fredriksson, Larsson et al 2006;Larsson and Strömberg 2006). In this study, an in-house Monte Carlo software (Fredriksson, Larsson et al 2006;2008a;2008b) that tracks and stores information about each and every photon, including individual Doppler shifts, scattering positions, and photon weights, was used. When simulating the LDPI system, a forced detection variance reduction technique was applied to accelerate the simulations (Meier, Lee et al 1978;Fredriksson, Larsson et al 2008b).…”

“…In this study, an in-house Monte Carlo software (Fredriksson, Larsson et al 2006;2008a;2008b) that tracks and stores information about each and every photon, including individual Doppler shifts, scattering positions, and photon weights, was used. When simulating the LDPI system, a forced detection variance reduction technique was applied to accelerate the simulations (Meier, Lee et al 1978;Fredriksson, Larsson et al 2008b). For both the LDPM and the LDPI simulations, the rotational symmetry of the tissue models was used to accelerate the simulations.…”

A Single Doppler Shift of Laser Doppler for Measured Average Velocity

“…When light is scattered by a moving object it will be frequency shifted depending on the movement of the object, the direction of the incoming light and the direction of the scattered light with velocity v (m/s) . The angular frequency shift, f D will then be [9]:…”