A simple analysis of extinction spectra of cancerous and normal prostate tissues in near infrared range using a size discrete particle distribution and Mie scattering model

The extinction spectra and optical coefficients of human cancerous and normal prostate tissues were investigated in the spectral range of 750 nm - 860 nm. The scattering coefficient (mu(s)) was determined from the extinction measurements on thin prostate tissue and Beer's law. The absorption coefficient (mu(a)) and the reduced scattering coefficient (mu(s)') were extracted from integrate sphere intensity measurements on prostate tissue of which the thickness is in the multiple scattering range. The anisotropy factor (g) was calculated using the extracted values of mu(s) and mu(s)'. A micro-optical model of soft biological tissue was introduced to simulate the numerical computation of the absolute magnitudes of its scattering coefficients from the refractive index and a particle distribution function based on the Mie theory. A key assumption of the model is that the refractive index variations caused by microscopic tissue elements can be treated as particles with sizes distributed according to a skewed log-normal distribution function. The particle distribution and mean particle size of the two types of tissues were then calculated. Results show that the mean diameter of the particle size of cancerous tissue is larger than that of the cancerous tissue, which is responsible for larger reduced scattering coefficient of normal tissue in comparison with cancerous tissue. The results can be explained the change of tissue during prostate cancer evolution defined by Gleason Grade. The difference of the particles distribution and optical coefficients of cancerous and normal prostate tissues may present a potential criterion for prostate cancer detection.