Proton nuclear magnetic resonance imaging as a predictor of the outcome of photodynamic therapy of tumours

The ability to monitor non-invasively and at early times, the cytotoxic efficacy of a cancer treatment in an individual subject, plainly of great potential clinical value. In a recent publication, Naruse et al (1986) showed proton nuclear magnetic resonance (NMR) images of a rat glioma that had been treated 48 h previously by radiofrequency (RF) hyperthermia. Regions of high signal intensity were readily distinguishable and were equated qualitatively with histological necrosis caused by the heat treatment. These increases in signal intensity almost certainly reflected an increase in water content associated with oedematous changes in the tumour. This might expected after in vivo hyperthermia, where an important contribution to the toxic effect is vascular collapse with subsequent secondary ischaemic necrosis of sheets of tumour cells (reviewed by Reinhold & Endrich, 1986). A similar form of damage occurs after photodynamic therapy (PDT), the combination of non-toxic photosensitizing drugs and non-thermal ...