Optical dosimetry in photodynamic therapy: determination of the effective penetration depth of light in tissue according to measurements in backscattering models

摘要

The extent of tumor necrosis can be determined by the knowledge of the penetration depth of the light through tissue. So, we must determine the effective penetration depth `$delta@' during treatment, depth at which the incident light intensity is reduced to 36.6%. Light transmission measurements through tissues is the experimental model usually used as a reference method to estimate the value of $delta@. In order to achieve subsequently on line and in situ light dosimetry during PDT, light backscattering has been studied in different concentrations of blue ink and intralipid-20%. All parameters which would influence the value of the back-attenuation coefficient $Sigma$-ba$/ have been reviewed separately. The results of transmission and backscattering measurements are compared. A correlation function `R' between $Sigma$-eff$/ and $Sigma$-ba$/ can be deduced, the knowledge of R allows us to determine the effective light penetration depth in tissue through backscattering measurement.