The pathologic and thermal effects of gold vapor laser photodynamic therapy on the larynx. Experimental study.

A gold vapor laser, which emits short pulses of light at a wavelength of 628 nm, was used to deliver varying amounts of energy (30 to 120 J/cm2) to the presensitized (dihematoporphyrin ether) canine larynx. Between 30 and 60 J/cm2, the larynx appeared normal, and when 70 to 100 J/cm2 was applied, only mild edema and erythema were seen. Simultaneously, a thermocouple probe was used and a 0.4 degrees C to 1.5 degrees C temperature rise found. Thus, the gold vapor laser seems capable of achieving the therapeutic photosensitizing effect without causing significant laryngeal edema or thermal activity.