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Proceedings Paper

Singlet oxygen explicit dosimetry to predict long-term local tumor control for BPD-mediated photodynamic therapy
Author(s): Michele M. Kim; Rozhin Penjweini; Yi Hong Ong; Timothy C. Zhu
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Paper Abstract

Photodynamic therapy (PDT) is a well-established treatment modality for cancer and other malignant diseases; however, quantities such as light fluence, photosensitizer photobleaching rate, and PDT dose do not fully account for all of the dynamic interactions between the key components involved. In particular, fluence rate (Φ) effects are not accounted for, which has a large effect on the oxygen consumption rate. In this preclinical study, reacted singlet oxygen [1O2]rx was investigated as a dosimetric quantity for PDT outcome. The ability of [1O2]rx to predict the long-term local tumor control rate (LCR) for BPD-mediated PDT was examined. Mice bearing radioactivelyinduced fibrosarcoma (RIF) tumors were treated with different in-air fluences (250, 300, and 350 J/cm2) and in-air ϕ (75, 100, and150 mW/cm2) with a BPD dose of 1 mg/kg and a drug-light interval of 3 hours. Treatment was delivered with a collimated laser beam of 1 cm diameter at 690 nm. Explicit dosimetry of initial tissue oxygen concentration, tissue optical properties, and BPD concentration was used to calculate [1O2]rx. Φ was calculated for the treatment volume based on Monte-Carlo simulations and measured tissue optical properties. Kaplan-Meier analyses for LCR were done for an endpoint of tumor volume ≤ 100 mm3 using four dose metrics: light fluence, photosensitizer photobleaching rate, PDT dose, and [1O2]rx. PDT dose was defined as the product of the timeintegral of photosensitizer concentration and Φ at a 3 mm tumor depth. Preliminary studies show that [1O2]rx better correlates with LCR and is an effective dosimetric quantity that can predict treatment outcome.

Paper Details

Date Published: 13 February 2017
PDF: 8 pages
Proc. SPIE 10047, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXVI, 100470X (13 February 2017); doi: 10.1117/12.2250435
Show Author Affiliations
Michele M. Kim, Univ. of Pennsylvania (United States)
Rozhin Penjweini, Univ. of Pennsylvania (United States)
Yi Hong Ong, Univ. of Pennsylvania (United States)
Timothy C. Zhu, Univ. of Pennsylvania (United States)

Published in SPIE Proceedings Vol. 10047:
Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXVI
David H. Kessel; Tayyaba Hasan, Editor(s)

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