Turzhitsky V, Rogers JD, Mutyal NN, Roy HK, Backman V.
Characterization of Light Transport in Scattering Media at Subdiffusion Length Scales with Low-Coherence Enhanced Backscattering. Ieee Journal of Selected Topics in Quantum ElectronicsIeee Journal of Selected Topics in Quantum ElectronicsIeee Journal of Selected Topics in Quantum Electronics. 2010;16 :619-626.
AbstractLow-coherence enhanced backscattering (LEBS) is a technique that has recently shown promise for tissue characterization and the detection of early precancer. Although several Monte Carlo models of LEBS have been described, these models have not been accurate enough to predict all of the experimentally observed LEBS features. We present an appropriate Monte Carlo model to simulate LEBS peak properties from polystyrene microsphere suspensions in water. Results show that the choice of the phase function greatly impacts the accuracy of the simulation when the transport mean free path (ls*) is much greater than the spatial coherence length (L(SC)). When ls* < L(SC), a diffusion-approximation-based model of LEBS is sufficiently accurate. We also use the Monte Carlo model to validate that LEBS can be used to measure the radial scattering probability distribution (radial point spread function), p(r), at small length scales and demonstrate LEBS measurements of p(r) from biological tissue. In particular, we show that precancerous and benign mucosal tissues have different small length scale light transport properties.
Radosevich AJ, Turzhitsky VM, Mutyal NN, Rogers JD, Stoyneva V, Tiwari AK, De La Cruz M, Kunte DP, Wali RK, Roy HK, et al. Depth-resolved measurement of mucosal microvascular blood content using low-coherence enhanced backscattering spectroscopy. Biomedical Optics ExpressBiomedical Optics ExpressBiomedical Optics Express. 2010;1 :1196-1208.
AbstractLow-coherence enhanced backscattering (LEBS) spectroscopy is a light scattering technique which uses partial spatial coherence broadband illumination to interrogate the optical properties at sub-diffusion length scales. In this work, we present a post-processing technique which isolates the hemoglobin concentration at different depths within a sample using a single spectroscopic LEBS measurement with a fixed spatial coherence of illumination. We verify the method with scattering (spectralon reflectance standard and polystyrene microspheres) and absorbing (hemoglobin) phantoms. We then demonstrate the relevance of this method for quantifying hemoglobin content as a function of depth within biological tissue using the azoxymethane treated animal model of colorectal cancer. (C)2010 Optical Society of America
Roy HK, Gomes AJ, Ruderman S, Bianchi LK, Goldberg MJ, Stoyneva V, Rogers JD, Turzhitsky V, Kim Y, Yen E, et al. Optical Measurement of Rectal Microvasculature as an Adjunct to Flexible Sigmoidosocopy: Gender-Specific Implications. Cancer Prevention ResearchCancer Prevention ResearchCancer Prevention Research. 2010;3 :844-851.
AbstractFlexible sigmoidoscopy is a robust, clinically validated, and widely available colorectal cancer screening technique that is currently sanctioned by major guideline organizations. Given that endoscopic visualization is generally limited to the distal third of the colon and women tend to have a proclivity for proximal lesions, the flexible sigmoidoscopy performance is markedly inferior in women than in men. Our group has shown that by using a novel light-scattering approach, we were able to detect an early increase in blood supply (EIBS) in the distal colonic mucosa, which served as a marker of field carcinogenesis and, hence, proximal neoplasia. Therefore, we sought to ascertain whether rectal EIBS would improve flexible sigmoidoscopy, especially in women. A polarization-gated spectroscopy fiber-optic probe was used to assess EIBS in the endoscopically normal rectum (n = 366). When compared with gender-matched neoplasia-free controls, females with advanced proximal neoplasia (n = 10) had a robust (60%; P = 0.002) increase in rectal mucosal oxyhemoglobin content whereas the effect size in males was less marked (33%; P = 0.052). In women, addition of rectal oxyhemoglobin tripled the sensitivity for advanced neoplasia over flexible sigmoidoscopy alone. Indeed, the performance characteristics seemed to be excellent (sensitivity, 100%; specificity, 76.8%; positive predictive value, 32.6%; and negative predictive value, 100%). A variety of nonneoplastic factors were assessed and did not confound the relationship between rectal EIBS and advanced neoplasia. Therefore, using rectal EIBS in combination with flexible sigmoidoscopy mitigated the gender gap and may allow flexible sigmoidoscopy to be considered as a viable colorectal cancer screening test in women. Cancer Prev Res; 3(7); 844-51. (C) 2010 AACR.
Turzhitsky V, Radosevich A, Rogers JD, Taflove A, Backman V.
A predictive model of backscattering at subdiffusion length scales. Biomedical Optics ExpressBiomedical Optics ExpressBiomedical Optics Express. 2010;1 :1034-1046.
AbstractWe provide a methodology for accurately predicting elastic backscattering radial distributions from random media with two simple empirical models. We apply these models to predict the backscattering based on two classes of scattering phase functions: the Henyey-Greenstein phase function and a generalized two parameter phase function that is derived from the Whittle-Matern correlation function. We demonstrate that the model has excellent agreement over all length scales and has less than 1% error for backscattering at subdiffusion length scales for tissue-relevant optical properties. The presented model is the first available approach for accurately predicting backscattering at length scales significantly smaller than the transport mean free path. (C) 2010 Optical Society of America