Intratumoural Light Distribution in an Experimental Mouse Tumour Irradiated by a Diffuse-light Irradiator Compared with Unilateral Helium-neon Light for Photodynamic Therapy

Summary

Investigations on dosimetry in photodynamic therapy (PDT) of experimental mouse tumours transplanted into the right hind leg revealed a significant variability in the fluence rate reaching tumour cells in different parts of the tumour when irradiated by a 50 mW collimated He—Ne laser. Based on intratumoural fibre-optical light measurements, a new irradiation source was constructed, in which variability in the radiant energy fluence rate between different parts of the solid tumour was reduced. The new diffuse-light irradiator was constructed basically from two concentric water chambers surrounded by three linear 3000 W xenon flash lamps. The outer chamber was an optical band filter, and the inner chamber contained a light-dispersing solution of lipid droplets which created an isotropic light field in which the tumours were submerged for PDT. Compared with unilateral He—Ne laser irradiation, an enhancement factor of 7·3 in radiance was obtained for the diffuse-light irradiator measured in the tumour. The new apparatus provides a nearly isotropic light field for in vivo experimental PDT.