Explicit dosimetry for photodynamic therapy: macroscopic singlet oxygen modeling

✍ Scribed by Ken Kang-Hsin Wang; Jarod C. Finlay; Theresa M. Busch; Stephen M. Hahn; Timothy C. Zhu

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 864 KB
• Volume: 3
• Category: Article
• ISSN: 1864-063X
• DOI: 10.1002/jbio.200900101

✦ Synopsis

Abstract

Singlet oxygen (^1^O~2~) is the major cytotoxic agent responsible for cell killing for type‐II photodynamic therapy (PDT). An empirical four‐parameter macroscopic model is proposed to calculate the “apparent reacted ^1^O~2~ concentration”, [^1^O~2~]~rx~, as a clinical PDT dosimetry quantity. This model incorporates light diffusion equation and a set of PDT kinetics equations, which can be applied in any clinical treatment geometry. We demonstrate that by introducing a fitting quantity “apparent singlet oxygen threshold concentration” [^1^O~2~]~rx, sd~, it is feasible to determine the model parameters by fitting the computed [^1^O~2~]~rx~ to the Photofrin‐mediated PDT‐induced necrotic distance using interstitially‐measured Photofrin concentration and optical properties within each mouse. After determining the model parameters and the [^1^O~2~]~rx, sd~, we expect to use this model as an explicit dosimetry to assess PDT treatment outcome for a specific photosensitizer in an in vivo environment. The results also provide evidence that the [^1^O~2~]~rx~, because it takes into account the oxygen consumption (or light fluence rate) effect, can be a better predictor of PDT outcome than the PDT dose defined as the energy absorbed by the photosensitizer, which is proportional to the product of photosensitizer concentration and light fluence. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)