In Vivo Light Dosimetry For Interstitial Photodynamic Therapy: Results Of Clinical Importance.

J. P.A. Marijnissen; A. A.C Versteeg; W. M. Star

doi:10.1117/12.978010

13 June 1989 In Vivo Light Dosimetry For Interstitial Photodynamic Therapy: Results Of Clinical Importance.

J. P.A. Marijnissen, A. A.C Versteeg, W. M. Star

Proceedings Volume 1065, Photodynamic Therapy: Mechanisms; (1989) https://doi.org/10.1117/12.978010
Event: OE/LASE '89, 1989, Los Angeles, CA, United States

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.

Citation Download Citation

J. P.A. Marijnissen, A. A.C Versteeg, and W. M. Star "In Vivo Light Dosimetry For Interstitial Photodynamic Therapy: Results Of Clinical Importance.", Proc. SPIE 1065, Photodynamic Therapy: Mechanisms, (13 June 1989); https://doi.org/10.1117/12.978010

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