Near-IR optical properties of canine prostate tissue using oblique-incidence reflectometry

Optical imaging systems utilizing near-infrared light sources such as optical coherence tomography (OCT) have recently been used for imaging the prostate gland. However, the optimal wavelength for deep imaging of the prostate has yet to be determined. The objective of this study is to determine the optimal near-infrared wavelength for OCT imaging of the prostate using a system that has the potential to be used in an in vivo model. An obliqueincidence single point measurement technique using a normal-detector scanning system was implemented to determine the absorption (μ_a) and reduced scattering coefficients (μ_'s) of fresh canine prostate tissue, ex vivo, from the diffuse reflectance profile of near-IR light as a function of source-detector distance. The effective attenuation coefficient (μ_eff) and optical penetration depth (OPD) were then calculated for near-IR wavelengths of 1064, 1307, and 1555 nm. A total of ten canine samples were used for this study. At wavelengths of 1064, 1307, and 1555 nm, the mean absorption coefficients measured 0.08 ± 0.03, 0.12 ± 0.04, and 0.23 ± 0.09 cm^-1, respectively. The mean reduced scattering coefficients measured 16.60 ± 0.95, 14.30 ± 1.14, and 10.98 ± 2.35 cm^-1. The effective attenuation coefficients were calculated to be 2.00, 2.28, and 2.78 cm^-1, yielding OPD's of 0.5, 0.44, and 0.36 cm at 1064, 1307, and 1555 nm. OCT imaging studies of the prostate may benefit from replacement of commonly used 1310 nm broadband light sources with 1064 nm sources.