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Published November 7, 2004 | public
Journal Article

Comparison of human skin opto-thermal response to near-infrared and visible laser irradiations: a theoretical investigation

Abstract

Near-infrared wavelengths are absorbed less by epidermal melanin, and penetrate deeper into human skin dermis and blood than visible wavelengths. Therefore, laser irradiation using near-infrared wavelengths may improve the therapeutic outcome of cutaneous hyper-vascular malformations in moderately to heavily pigmented skin patients and those with large-sized blood vessels or blood vessels extending deeply into the skin. A mathematical model composed of a Monte Carlo algorithm to estimate the distribution of absorbed light, numerical solution of a bio-heat diffusion equation to calculate the transient temperature distribution, and a damage integral based on an empirical Arrhenius relationship to quantify the tissue damage was utilized to investigate the opto-thermal response of human skin to near-infrared and visible laser irradiations in conjunction with cryogen spray cooling. In addition, the thermal effects of a single continuous laser pulse and micropulse-composed laser pulse profiles were compared. Simulation results indicated that a 940 nm wavelength induces improved therapeutic outcome compared with a 585 and 595 nm wavelengths for the treatment of patients with large-sized blood vessels and moderately to heavily pigmented skin. On the other hand, a 585 nm wavelength shows the best efficacy in treating small-sized blood vessels, as characterized by the largest laser-induced blood vessel damage depth compared with 595 and 940 nm wavelengths. Dermal blood content has a considerable effect on the threshold incident dosage for epidermal damage, while the effect of blood vessel size is minimal. For the same macropulse duration and incident dosage, a micropulse-composed pulse profile results in higher peak temperature at the basal layer of skin epidermis than an ideal single continuous pulse profile.

Additional Information

© 2004 IOP Publishing Ltd. Received 4 July 2004; Published 8 October 2004. This study was supported in part by a grant from the Institute of Arthritis and Musculoskeletal and Skin Disease (IR01-AR47996) at the National Institutes of Health to Dr Bahman Anvari. We thank Dr James W Tunnell from G R Harrison Spectroscopy Laboratory at Massachusetts Institute of Technology for fruitful discussions.

Additional details

Created:
August 19, 2023
Modified:
October 23, 2023