Preclinical studies of photodynamic therapy of intracranial tissues

Lothar D. Lilge; Marja Sepers; Jane Park; Cindy O'Carroll; Poupak Pournazari; Joe Prosper; Brian C. Wilson

doi:10.1117/12.273488

8 May 1997 Preclinical studies of photodynamic therapy of intracranial tissues

Lothar D. Lilge, Marja Sepers, Jane Park, Cindy O'Carroll, Poupak Pournazari, Joe Prosper, Brian C. Wilson

Proceedings Volume 2972, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy VI; (1997) https://doi.org/10.1117/12.273488
Event: BiOS '97, Part of Photonics West, 1997, San Jose, CA, United States

Abstract

The applicability and limitations of the photodynamic threshold model were investigated for an intracranial tumor (VX2) and normal brain tissues in a rabbit model. Photodynamic threshold values for four different photosensitizers, i.e., Photofrin, 5(delta) -aminolaevulinic acid (5(delta) -ALA) induced Protoporphyrin IX (PPIX), Tin Ethyl Etiopurpurin (SnET₂), and chloroaluminum phthalocyanine (AlClPc), were determined based on measured light fluence distributions, macroscopic photosensitizer concentration in various brain structures, and histologically determined extent of tissue necrosis following PDT. For Photofrin, AlClPc, and SnET₂, normal brain displayed a significantly lower threshold value than VX2 tumor. For 5(delta) -ALA induced PPIX and SnET₂ no or very little white matter damage, equalling to very high or infinite threshold values, was observed. Additionally, the latter two photosensitizers showed significantly lower uptake in white matter compared to other brain structures and VX2 tumor. Normal brain structures lacking a blood- brain-barrier, such as the choroid plexus and the meninges, showed high photosensitizer uptake for all photosensitizers, and, hence, are at risk when exposed to light. Results to date suggest that the photodynamic threshold values iares valid for white matter, cortex and VX2 tumor. For clinical PDT of intracranial neoplasms 5(delta) -ALA induced PPIX and SnET₂ appear to be the most promising for selective tumor necrosis.However, the photosensitizer concentration in each normal brain structure and the fluence distribution throughout the treatment volume and adjacent tissues at risk must be monitored to maximize the selectivity of PDT for intracranial tumors.

Citation Download Citation

Lothar D. Lilge, Marja Sepers, Jane Park, Cindy O'Carroll, Poupak Pournazari, Joe Prosper, and Brian C. Wilson "Preclinical studies of photodynamic therapy of intracranial tissues", Proc. SPIE 2972, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy VI, (8 May 1997); https://doi.org/10.1117/12.273488

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