A comparison of two probes to determine rectum optical properties

Andrew C. Li; Yi Hong Ong; Celina Li; Jie He; Andreea Dimofte; Theresa M. Busch; Brian C. Wilson; Robert Weersink; Timothy C. Zhu

doi:10.1117/12.2582395

12 March 2021 A comparison of two probes to determine rectum optical properties

Andrew C. Li, Yi Hong Ong, Celina Li, Jie He, Andreea Dimofte, Theresa M. Busch, Brian C. Wilson, Robert Weersink, Timothy C. Zhu

Author Affiliations +

Proceedings Volume 11628, Mechanisms and Techniques in Photodynamic Therapy and Photobiomodulation; 1162808 (2021) https://doi.org/10.1117/12.2582395
Event: SPIE BiOS, 2021, Online Only

Abstract

Tissue optical properties are crucial for determining the light dose delivered to the tumor. Two probes are compared: the two-catheter probe is based on transmittance measurement between one point source and one isotropic detector inside parallel catheters spaced at 0.5 cm along a 1-inch diameter transparent cylinder; and a 1-inch trans-rectal diffuse optical tomography (DOT) probe designed for prostate measurements, using a multiple fiber-array with source-detector separations of 1.4-10 mm. The two-catheter probe uses an empirical model for primary and scatter light fluence rates in the cylindrical cavity condition for anal PDT to determine optical properties along the source catheter using dual motors to move the source and detector along the catheters. The DOT probe uses finite element method (FEM) to obtain distribution of optical properties in 3D. Validations for the two probes were performed in liquid and solid phantoms. For each method, validation was performed in tissue-mimicking liquid phantoms for a range of known optical properties (μ_abetween 0.05 and 0.9 cm^-1 and μ_s’ between 5.5 and 16.5 cm^-1). To cross-check the two methods, solid phantoms were created of known optical properties at the University of Pennsylvania and sent for measurement to Princess Margaret Cancer Centre (PMH) to mimic realistic patient simulating conditions. Measurements were taken and optical properties were then recovered without knowing the expected values to cross-validate each probe. The results show modest agreement between the measured μ_a and μ_s’values, but high degree of agreement between the measured μ_effperformed independently using the two methods.

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Citation Download Citation

Andrew C. Li, Yi Hong Ong, Celina Li, Jie He, Andreea Dimofte, Theresa M. Busch, Brian C. Wilson, Robert Weersink, and Timothy C. Zhu "A comparison of two probes to determine rectum optical properties", Proc. SPIE 11628, Mechanisms and Techniques in Photodynamic Therapy and Photobiomodulation, 1162808 (12 March 2021); https://doi.org/10.1117/12.2582395

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