AbstractID: 6933 Title: Interstitial light distribution at 730nm prostate photodynamic therapy
Light distribution in tissue is important for dosimetry of prostate photodynamic therapy
(PDT). In this study we measured the light fluence distribution for 730-nm in optical
phantoms. A 0.3-mm diameter isotropic detector with scattering tip was used to measure
the light fluence rate. Two different type of phantoms were used to simulate prostates:
liquid phantoms composed of intralipid and green ink and solid prostate shaped phantoms
made of silicon gel with TiO2 and C mixture. The light sources used were point and
linear sources. We used three different absorption coefficients (.01, .03 and .05 cm-1), and
two scattering coefficients (5 and 10 cm-1). We found that µa is proportional to the
concentration of green ink with the proportionality constant equal to 7.182 and µs is
proportional to the concentration of intralipid with the proportionality constant equal to
2092. When using the point source, the fluence rate agrees with the diffusion
approximation equation: φ=sµeff2 e-µeff r/4πµar , where µa and µeff are the absorption and
the effective coefficients and s is the total power of the point source. The light fluence for
the linear source agrees with the diffusion approximation, provided the light power
density distribution of the linear fiber is individually optimized. In conclusion, we have a
realistic knowledge about what is the light fluence distribution inside the prostate,
information that can be used to quantitatively estimate light fluence distribution for
prostate PDT.