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Comparison between isotropic and nonisotropic dosimetry systems during intraperitoneal photodynamic therapy
T G Vulcan1, T C Zhu, C E Rodriguez
1Department of Physics and Astronomy University of Pennsylvania, Philadelphia, Pennsylvania 19104-4283, USA.
Background And Objective:
On-line monitoring of light fluence during intraperitoneal photodynamic therapy (IP PDT) is crucial for safe light delivery. A flat photodiode-based dosimetry system is compared with an isotropic detector-based system in patients undergoing IP PDT.
Study Design/Materials And Methods:
Flat photodiodes and spherical detectors were placed side by side in the abdomen, for simultaneous light dosimetry in 19 patients. Tissue phantom experiments were performed to provide a preliminary estimate of the tissue optical properties of the peritoneum.
Results:
The conversion factor between systems for 630-nm light was found to be 1.7 +/- 0.12. The mu(eff) of the tissues in the abdomen is estimated to vary between 0.5 cm(-1) to 1.4 cm(-1) assuming a mu(s)' = 7 cm(-1).
Conclusions:
The measured conversion factor should allow for comparison of light fluences with future clinical protocols that use an isotropic-based detector system. Differences in the optical properties of the underlying tissues may contribute to the variability in light measurements.