Comparison between isotropic and nonisotropic dosimetry systems during intraperitoneal photodynamic therapy |
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Authors: | Vulcan T G Zhu T C Rodriguez C E Hsi A Fraker D L Baas P Murrer L H Star W M Glatstein E Yodh A G Hahn S M |
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Affiliation: | Department of Physics and Astronomy University of Pennsylvania, Philadelphia, Pennsylvania 19104-4283, USA. |
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Abstract: | 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. |
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