27 February 2007 Conformal light delivery using tailored cylindrical diffusers
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Tailored light diffusers offer the flexibility of shaping the delivered light dose (fluence rate) distribution, potentially leading to conformal light delivery. Because of scattering and absorption, tissue acts as a spatial low pass filter of the diffuser's emission profile, and therefore some dose distributions with high spatial frequencies cannot be delivered. We characterize the set of attainable light dose distributions in terms of the spatial frequency of the emission profile and identify regimes where such distributions are less sensitive to changes in optical properties. Furthermore, we contrast two different algorithms to solve the inverse problem: Simulated Annealing (SA) and Non-negative Least Squares (NNLS). SA is plagued by superimposed high frequency components that do not contribute significantly to the cost. We present an iterative low pass filter that smooths the emission profile without considerably increasing the cost. A non-negative least square (NNLS) algorithm is also tested. We conclude that non-negative least squares (NNLS) is superior to simulated annealing (SA) in terms of time performance and cost minimization.
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A. Rendon, A. Rendon, J. Okawa, J. Okawa, R. Weersink, R. Weersink, J. C. Beck, J. C. Beck, Lothar Lilge, Lothar Lilge, "Conformal light delivery using tailored cylindrical diffusers", Proc. SPIE 6427, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XVI, 64270M (27 February 2007); doi: 10.1117/12.700996; https://doi.org/10.1117/12.700996

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