The selective photothermolysis, SPT, model to explain light and tissue interaction was first publicly proposed in 1983. The model illustrates the important role of selective absorption and thermal diffusion and has led to an understanding of how clinical protocols using laser radiation should be designed to optimize therapy. SPT concepts have been used to develop clinical protocols for the treatment of abnormal vascular and pigmented lesions and tattoos. Commercial devices built to use these protocols have gained market acceptance. Laser hardware needs further improvement because state-of-the-art devices do not produce the optimum pulse durations for the treatment of ectatic vascular lesions. Pulse durations from commercial dye lasers used for the treatment of port wine stain birthmarks are limited to 400 microseconds. The SPT model requires pulse durations closer to 4 milliseconds for the optimized treatment of 100 micron diameter vessels or larger. All clinical indications show that longer pulses fitting the needs of SPT would greatly improve clinical end points and better treat larger vessels. It is believed that longer pulses will help in the treatment of telangiectasia of the lower limbs, the leg vein problem which is reputed to have a large commercial significance.
