Signal dependence and noise source in ultrasound-modulated optical tomography

Abstract

A Monte Carlo modeling technique was used to simulate ultrasound-modulated optical tomography in inhomogeneous scattering media. The contributions from two different modulation mechanisms were included in the simulation. Results indicate that ultrasound-modulated optical signals are much more sensitive to small embedded objects than unmodulated intensity signals. The differences between embedded absorption and scattering objects in the ultrasound-modulated optical signals were compared. The effects of neighboring inhomogeneity and background optical properties on the ultrasoundmodulated optical signals were also studied. We analyzed the signal-to-noise ratio in the experiment and found that the major noise source is the speckle noise caused by small particle movement within the biological tissue sample. We studied this effect by incorporating a Brownian motion factor in the simulation.

Optical and mechanical properties in photorefractive crystal based ultrasound-modulated optical tomography

“…The BSO was selected because of its relatively large two-wave mixing gain compared with a semiconductor crystal (such as GaAs). Though the response time of the BSO, 100~200 ms in our experimental conditions, was relatively long compared with GaAs, it was still comparable to the speckle correlation time of 2 cm in the ex vivo chicken breast tissue 21 . To enhance the two-way mixing gain and reduce heating on the crystal, 22 a 1 KHz square wave of 8 KV/cm peak-to-peak was applied.…”

Fast Monte Carlo simulations of ultrasound-modulated light using a graphics processing unit

“…One of the main reasons for the popularity of Wang's ultrasoundmodulated light ͑UL͒ model is that it is built on a MC light transport model widely used in biomedical optics, known as MCML, by Wang et al 14 Another advantage is that the MC model is accompanied by an analytical solution 8,15 allowing for validation of the simulation. Subsequent MC models by Wang's group consider more realistic scenarios, allowing optical inhomogenities, and cylindrical 16 and focused ultrasound 17 modulation. In the past few years, MC simulations in general have undergone a dramatic speed improvement unleashed by the availability of low-cost graphics cards utilizing a new architecture known as Compute Unified Device Architecture ͑CUDA͒.…”

Correlation transfer equation for multiply scattered light modulated by an ultrasonic pulse

“…In addition, based on the theoretical models, Monte Carlo algorithms were developed and used for comparison with the theoretical predictions [23,25,33,34,39] as well as for modeling the scattering samples that have optically absorbing objects of cylindrical shapes [40].…”