Thermal damage of blood vessels in a rat skin-flap window chamber using indocyanine green and a pulsed alexandrite laser: A feasibility study

Abstract

The design criteria and feasibility of specifically targeting blood vessels for thermal damage by using a pulsed alexandrite infra-red laser to heat an intravascularly injected infra-redabsorbing dye, namely indocyanine green (ICG), is demonstrated. Theoretical calculations map the distribution of light and heat in and around the subcutaneous blood vessels in a rat skin-flap window chamber as functions of dye concentration, vessel size, and vessel depth. Theoretical calculations showed that an injected dose of 6–24 mgkg⁻¹ of ICG and a 120-μs, 1-J cm⁻² alexandrite laser pulse at a wavelength of 785 nm would be sufficient to achieve selective vascular damage to a depth of at least 0.15 cm. Feasibility experiments were performed which illustrated that an irradiation of 1.27 J cm⁻² of skin flaps in uninjected control rats showed no evidence of vascular damage while vascular damage was seen in skin flaps using an experimental protocol of 12 mg kg⁻¹ i.v. of ICG and an energy fluence of 0.76 J cm⁻². This procedure could conceivably prove useful in the treatment of vascular lesions or cancer.