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-red- absorbing 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 mg kg -1 of ICG and a 120 µ s, 1 Jcm -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 irridiation of 1.27 Jcm -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 mgkg -1 i.v. of ICG and an energy fluence of 0.76 Jcm -2 . This procedure could conceivably prove useful in the treatment of vascular lesions or cancer.
S. T. Flock, S. L. Jacques, "Thermal Damage of Blood Vessels in a Rat Skin-flap Window Chamber Using Indocyanine Green and a Pulsed Alexandrite Laser: A Feasibility Study," Lasers in Medical Science,8, 185-196 (1993).