Chapter 52: Laser and Light-Based Treatment of Vascular Lesions

INTRODUCTION

Vascular lesions are a commonly encountered problem in procedural dermatology, and patients frequently desire their removal. Light-based devices such as lasers and intense pulsed light (IPL) are among the most utilized technologies for removal of these lesions. This chapter will discuss the evolution of light-based therapies, the treatment of vascular lesions using the principles of photothermolysis, and will review diagnostic criteria and suggested treatments for many vascular lesions including port wine stain (PWS) birthmarks, infantile hemangiomas (IHs), venous malformations (VMs), telangiectasias and rosacea, cherry and spider angiomas, poikiloderma of Civatte, and angiokeratomas.

LIGHT DEVICES USED TO TREAT VASCULAR LESIONS

One of the first indications for the use of lasers in dermatologic surgery was for the treatment of vascular lesions. In 1968, the argon laser was one of the first lasers used to treat PWS and IH.¹ The argon laser is a continuous wave laser that produces blue-green light from 488 to 514 nm. The blue-green light is preferentially absorbed by its complementary color, red. It is thus absorbed by hemoglobin in the superficial vessels of vascular lesions.² It is this heating of the blood vessels that leads to thermal damage and thrombosis, which can be demonstrated on histology.³ Although the argon laser, and other continuous and quasi-continuous wave lasers such as the copper vapor, krypton-ion, argon-pumped dye, and carbon dioxide lasers, improved the color of the vascular lesions, they also caused a large amount of nonselective heating due to long pulse durations and unwanted absorption by epidermal melanin. Scarring and dyspigmentation were common. These lasers are no longer used for treatment of vascular lesions, as the theory of selective photothermolysis revolutionized the use of lasers for treatment of skin lesions.

The theory of selective photothermolysis, defined in 1983 by Anderson and Parrish, comprises three governing principles.⁴ The first principle is to select a wavelength that has a greater optical absorption by the target chromophore than by the surrounding tissue. Secondly, the pulse duration should be matched to the thermal relaxation time of the target chromophore. The thermal relaxation time is defined as the time required for the heat, which is generated within the chromophore by the absorbed light, to cool to one-half of the original temperature. The thermal relaxation time is directly proportional to the square of the diameter of the target and inversely proportional to the thermal diffusivity of the tissue. Larger target chromophores should be targeted with longer pulse durations, whereas smaller chromophores necessitate shorter pulse durations. Pulse durations that are longer than the thermal relaxation time of the target chromophore tend to create more heat than can be absorbed by the target chromophore. This extra heat diffuses away from the target chromophore and creates generalized nonselective heating of the surrounding tissue. The final principle is the need for a fluence that will treat the target chromophore, but will minimize nonspecific thermal related injury.^...