Action Spectrum of Vascular Specific Injury Using Pulsed Irradiation

It has been clearly demonstrated that cutaneous blood vessels will be selectively damaged by a laser whose wavelength matches one of the three absorption spectral peaks of the chromophore, oxyhemoglobin, for example, 577nm. A restriction in the application of this wavelength for the treatment of benign cutaneous vascular tumors, such as portwine stains, has been the penetration depth of 577nm irradiation of approximately 0.5mm from the dermal epidermal junction (DEJ). This study was undertaken to establish whether it was possible to increase the penetration depth from 0.5mm by changing the wavelength to beyond 577nm in albino pig skin. Results from this study confirm that penetration depth increases from 0.5 to 1.2mm by changing the wavelength from 577 to 585nm at 4 J/c2, while maintaining the same degree of vascular selectivity as that previously described after 577nm irradiation. This occurred in spite of a mismatch in the wavelength between 585nm and the oxyhemoglobin absorption peak of 577nm. Unlike 585nm irradiation and in contrast with cheoretical predictions, 590nm laser light did not penetrate as deeply as 585nm. Not only was there a reduction in the penetration of the laser beam from 1.2mm at 585nm to 0.8mm at 590nm, at 4 J/cm2, but there was also a decrease in vascular selectivity in albino pig skin exposed to 590nm irradiation.