THERMAL IMAGING DURING PHOTODYNAMIC THERAPY (PDT)

This study was designed to measure the PDT associated changes in tumour tissue temperature and to calculate if tumoricidally relevant hyperthermia might be induced by the current clinically used PDT modalities. Syrian golden hamsters with amelanotic melanomas (A-Mel-3) received intravenous injections of Photofrin II (5 mg kg−1 b.w.) or 0.9% sodium chloride (2 ml kg−1 b.w.). Twenty-four hours later tumour surface and tumour centre temperature were quantified by an infra-red sensitive thermal imaging device and an implanted thermal probe during laser treatment at a wavelength of 630 nm. With laser light irradiation using power densities of 100 mW cm−2 or 200 mW cm−2, a significant temperature increase was noted in comparison to the baseline values. At total energy delivery of 100 J cm−2 the tumoricidally relevant threshold of 43°C was exceeded with 200 mW cm−2 only. However, no significant temperature differences were measured between photosensitized and control tumours receiving 100 mW cm−2 or 200 mW cm−2. Calculation of the corresponding applied hyperthermic dose revealed that submaximum hyperthermic effects were involved with irradiation intensities of 200 mW cm−2. © 1992, Baillière Tindall. All rights reserved.