Effect of thermal changes on optical properties in fresh and previously frozen prostate tissue

William H. Nau; Robert J. Roselli; Douglas F. Milam M.D.

doi:10.1117/12.275079

22 May 1997 Effect of thermal changes on optical properties in fresh and previously frozen prostate tissue

William H. Nau, Robert J. Roselli, Douglas F. Milam M.D.

Proceedings Volume 2970, Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems VII; (1997) https://doi.org/10.1117/12.275079
Event: BiOS '97, Part of Photonics West, 1997, San Jose, CA, United States

Abstract

The deposition, and distribution of light in laser irradiated tissue are important in determining the extent of tissue injury during laser prostatectomy. As tissue is irradiated, the optical properties change as a function of temperature due to an alteration of molecular and cellular structure. An increase in the absorption or scattering coefficient may prevent light from penetrating deeper into tissue, thus compromising laser treatment. The purpose of this study was to determine if temperature affects the optical scattering and absorption coefficients of canine prostate tissue. The effects of freezing of tissue prior to measurement were also investigated. A double integrating sphere spectrophotometer was used to measure reflectance, and transmittance of laser light in canine prostate at two wavelengths. Optical properties were calculated using an inverse adding-doubling algorithm. Measurements were made on samples heated for ten minutes in a waterbath at 10 degree increments from 35 to 55 degrees Celsius, and 5 degree increments from 60 to 85 degrees Celsius. In general, absorption and anisotropy coefficients decreased slightly with increasing exposure temperature up to 65 degrees Celsius, then increased sharply. Scattering coefficients increased slowly from the baseline temperature to 60 degrees Celsius, followed by a sharp increase between 60 and 70 degrees Celsius. The scattering coefficient appeared to decrease at higher temperatures. Freezing the tissue prior to making the measurements resulted in a higher estimate of (mu) _a, (mu) _s, and g. These results were also found to be dependent upon the wavelength investigated. Results from this study indicate that as tissue is coagulated, thermally induced changes in the optical properties will limit the depth of penetration of light into the tissue.

Citation Download Citation

William H. Nau, Robert J. Roselli, and Douglas F. Milam M.D. "Effect of thermal changes on optical properties in fresh and previously frozen prostate tissue", Proc. SPIE 2970, Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems VII, (22 May 1997); https://doi.org/10.1117/12.275079

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