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Proceedings Paper

In Vivo Light Dosimetry For Interstitial Photodynamic Therapy: Results Of Clinical Importance.
Author(s): J. P.A. Marijnissen; A. A.C Versteeg; W. M. Star
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Paper Abstract

Effective treatment of non-superficial tumors using HpD-PDT requires the development of interstitial light application. In order to determine the efficacy of interstitial HpD-PDT, a dose effect relationship has been established in a rat rhabdomyosarcoma. Because of the lack of data about the light distribution in tissue a miniature isotropic light detector was used throughout this study for in vitro and in vivo light dosimetry, permitting evaluation of tumor response versus "light dose" (i.e. light energy fluence) distribution. Effects of increased light absorption due to the photosensitizer concentration in the tumor tissue were observed and taken into account in reporting the light dose throughout the tumor volumes. Light dosimetry during HpD-PDT treatments was performed as a check on the prescribed calculated light dose levels. Measurements demonstrate a gradual but drastic decrease in light penetration, beginning almost immediately after the start of the treatment. This phenomenon, which is also observed in clinical HpD-PDT treatments, complicated the assessment of the required light energy fluence for tumor control. The dose-effect experiments show that a high tumor control rate is achievable in a single HpD-FDT treatment. Failures were strongly correlated with inadequate light dose or light dose distribution. Successful treatment appeared to be highly dependent on the light dose at the tumor periphery. Vascular damage in a small margin of the surrounding normal tissue seems to be required. This implies that tumor treatment selectivity is mainly determined by restricted light penetration in tissues irradiated by local light application.

Paper Details

Date Published: 13 June 1989
PDF: 6 pages
Proc. SPIE 1065, Photodynamic Therapy: Mechanisms, (13 June 1989); doi: 10.1117/12.978010
Show Author Affiliations
J. P.A. Marijnissen, Dr. Daniel den Hoed Cancer Center (The Netherlands)
A. A.C Versteeg, Dr. Daniel den Hoed Cancer Center (The Netherlands)
W. M. Star, Dr. Daniel den Hoed Cancer Center (The Netherlands)

Published in SPIE Proceedings Vol. 1065:
Photodynamic Therapy: Mechanisms
Thomas J. Dougherty, Editor(s)

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