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Journal of Biomedical Optics • Open Access

Explicit dosimetry for 2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-a-mediated photodynamic therapy: macroscopic singlet oxygen modeling
Author(s): Rozhin Penjweini; Baochang Liu; Michele M. Kim; Timothy C. Zhu

Paper Abstract

Type II photodynamic therapy (PDT) is based on the photochemical reactions mediated through an interaction between a photosensitizer, ground-state oxygen ([3O2]), and light excitation at an appropriate wavelength, which results in production of reactive singlet oxygen ([1O2]rx). We use an empirical macroscopic model based on four photochemical parameters for the calculation of [1O2]rx threshold concentration ([1O2]rx,sh) causing tissue necrosis in tumors after PDT. For this reason, 2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-a (HPPH)-mediated PDT was performed interstitially on mice with radiation-induced fibrosarcoma (RIF) tumors. A linear light source at 665 nm with total energy released per unit length of 12 to 100  J/cm and source power per unit length (LS) of 12 to 150  mW/cm was used to induce different radii of necrosis. Then the amount of [1O2]rx calculated by the macroscopic model incorporating explicit PDT dosimetry of light fluence distribution, tissue optical properties, and HPPH concentration was correlated to the necrotic radius to obtain the model parameters and [1O2]rx,sh. We provide evidence that [1O2]rx is a better dosimetric quantity for predicting the treatment outcome than PDT dose, which is proportional to the time integral of the products of the photosensitizer concentration and light fluence rate.

Paper Details

Date Published: 24 December 2015
PDF: 9 pages
J. Biomed. Opt. 20(12) 128003 doi: 10.1117/1.JBO.20.12.128003
Published in: Journal of Biomedical Optics Volume 20, Issue 12
Show Author Affiliations
Rozhin Penjweini, The Univ. of Pennsylvania Health System (United States)
Baochang Liu, Univ. of Pennsylvania (United States)
Michele M. Kim, Univ. of Pennsylvania School of Medicine (United States)
Timothy C. Zhu, The Univ. of Pennsylvania Health System (United States)

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