Spectral power distributions of radiation sources used in phototherapy and photochemotherapy

Abstract

Much attention is focused on the amount of radiant energy emitted by treatment systems used in phototherapy and photochemotherapy; however, another important property of a radiation source, the spectral power distribution (SPD), has often been ignored. Measurement of the SPDs of various radiation sources produced unexpected findings. The SPDs of fluorescent bulbs promoted specifically for use in psoralen and ultraviolet A (PUVA) therapy was fairly uniform. However, of three blacklight bulbs that also may be used for PUVA therapy, each had a different SPD, and one of these bulbs emitted more than 90% of its energy in the ultraviolet (UV) wave band at wavelengths >360 nm. The wavelengths emitted by sunlamp fluorescent bulbs and an Alpine UV lamp, both of which are used for phototherapy, were predominantly <320 nm. A fluorescent bulb recently introduced for phototherapy had an SPD that was different from that of a PUVA bulb and from that of a sunlamp bulb, with a high emission in the 300- to 340-nm wave band. These findings indicate that consideration of both the SPD and the irradiance of a radiation source is necessary to determine its suitability for phototherapy or photochemotherapy.