A possible new incoherent lamp for photodynamic treatment of superficial skin lesions.

Since coherence of laser light is not necessary for photodynamic therapy of skin lesions, attempts have been made to construct incoherent lamps. A recent development is the PDT 1200 (Waldmann Medizintechnik/Germany), a light source consisting of a 1200 watt metal halogen lamp. Emission of 600 to 800 nm radiation is achieved by using cut-off filters. Power density can be varied from 30 mW/cm2 to 200 mW/cm2 in an area from 100 to 300 cm2. Biological effectiveness was proved by comparison with the radiation of an argon-pumped dye laser (Kiton red) emitting light at 630 nm. Three human cell lines were incubated with photofrin at different concentrations. After irradiation, cell viability was tested (MTT assay). Results proved biological effectiveness of the light source PDT 1200. No significant difference in cell viability was detected using either concentration of sensitizer. Therefore, we believe that PDT 1200 is a promising new light source for photodynamic therapy of skin lesions.