4.2.2.1 Vascular Lesions
In the quest for better vessel treatments, the past twenty years has brought us nearly twenty separate types of light-based technology, all with varying degrees of success. In the case of treating facial vessels and telangiectasias, there has been no universally consistent system. Gold standards in the past few years have typically been PDLs (Candela V-Beam), pulsed light systems with contact cooling and light filters in the 500 nm range (Palomar Starlux with Lux G hand piece), and to a lesser degree, potassium titanyl phosphate (KTP) lasers. Although the KTP laser has decreased in popularity in the past five years, several companies still make very nice systems that have produced some remarkable results, and are still widely used in top practices worldwide (Laserscope Aura/Gemini).
When dealing in the 500-600 nm wavelength range, several factors come into play. One is the high level of oxyhemoglobin absorption, which is our main goal in the treatment of any blood vessel, regardless of size or location. The absorption levels are highest in the lower end of the spectrum. Another factor to consider is competing chromophores, such as melanin. At these wavelengths, there is a high melanin absorption coefficient, so any energy that is directed toward the oxyhemoglobin in the vessels will be diluted by the melanin that lies above it. For that reason, most original vascular lasers (pulsed dye) are up at 585-600 nm, where the melanin absorption coefficient is lowest, but there is still a good amount of blood absorption. The KTP wavelength (at 532 nm) was thought to be too shallow a penetration, as a result of the high melanin absorption coefficient mentioned earlier.
A KTP laser is an Nd:YAG (neodymium:yttrium aluminum garnet) laser at a fundamental wavelength of 1,064 nm which is frequency doubled to half the wavelength or 532 nm by passing the beam through a KTP crystal. This setup, putting the system at 532 nm, created an extremely efficient pigmentation removal laser, and also a system that could attack the more superficial facial vessels. As the principles of light show us, the absorption coefficients at this wavelength for competing chromophores (melanin) are too high to obtain any real significant penetration. Certain early studies done by Van Gemart [3], however, show significant thermal damage at 1.4 mm, which almost contradicts physics because of the high level of melanin absorption at that wavelength. The reasons and mechanisms for this penetration are still debatable.
During treatments of facial vessels and telangiectasias with the KTP laser systems, vessel size is really the greatest deciding factor in treatment technique. The difference in vessel size dictates the pulse duration and the fluence (energy) that is used for the treatment. For larger vessels, longer pulse durations and higher fluences are typically used, while smaller vessels are treated by shorter pulse durations. The smaller vessels <0.3 mm (Fig. 4.3) are generally treated using the 4-6 mm spot sizes, and anywhere from 9-13 J/cm2
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Before After Figure 4.3 Treatment of smaller vessels (<0.3 mm) with the Palomar Lux G hand piece. |
with a pulse duration of 10-30 ms. Larger vessels >0.4 mm often respond better to the pulse durations in the 30-50 ms range, as it takes longer for the energy to evenly distribute itself around the vessel lining. For these types of individual distinct vessels, the tracing technique is used, where the vessel is traced with slightly overlapping pulses. For general redness and erythema associated with rosacea, the 10 mm spot size is used to easily treat the whole area of vessels.