Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3727_Библиотеки_им_академика_М_И_Перельмана

The use of laser technology in medicine has made tremen­dous advancements in recent years and continues to have a signicant impact on virtually every aspect of our lives. The word “laser” refers to light amplication by stim­ulated emission of radiation. It was Albert Einstein who rst proposed the theory of stimulated emission in 1917, which led to the discovery of the laser. The rst laser device was then created in 1960 by Theodore Maiman at Hughes Research Laboratories in Malibu, California, using syn­thetic ruby crystals as the lasing medium (5). A laser con­sists of three basic components: (1) the active medium (or laser gain medium), which is a solid, liquid, or gas material that absorbs external energy and raises some electrons into higher-energy states and emits photons thanks to its abil­ity to switch between energy levels; (2) an energy source, called the pumping device, that provides the necessary electrical or light (or another laser) energy for exciting the lasing medium; and (3) a resonant cavity, which is a system of mirrors placed around the gain medium that lters and amplies the light emitted from the excited atoms within the medium (Figure 43.1). One of the mirrors is a partial reec­tor (called an optical coupler), allowing some of the light to exit the laser device. The laser wavelength is represented by the symbol λ, with units of nm; it is primarily determined by the gain medium and the design of the resonant cavity. Lasers produce coherent light, where all photons have the same frequency, allowing them to create beams with very narrow wavelength spectrums. It is this characteristic that distinguishes lasers from other common sources of light, such as light bulbs, which emit photons in a wide range of wavelengths and directions, thus incoherent light. Watts (joules/second) are used to measure energy consumption (power). Energy consumption is determined by the product of power output and treatment duration (watt × seconds). Linear endovenous energy density (LEED) is dened as the amount of energy delivered over a dened distance within the treated vein, which is measured in joules/centimeter. It

part of the popliteal fossa between the heads of the gastroc­nemius muscle (Figure 43.6) given its anatomic variability and proximity to deeper neurovascular structures.

for persistent or recurrent symptoms should be assessed after 3 months for patients who are unable to receive a combined EVLA plus tributary treatment during the index procedure (4).

In most cases, the rst 1–2 cm of the vein beyond the SFJ or SPJ remains patent following EVLA. In early studies, occlusion rates were reported to be 95%–100% during the short term (1, 2, 24). Some veins never occlude, while oth­ers occlude on short-term follow-up but recanalize after some time, with most recanalizations occurring within 6–12 months (25).

Malskat et al. (28) sought to identify short- and long­term differences in the success rates of EVLA devices and techniques. They conducted a meta-analysis of 28 ran­domized controlled studies published between 2005 and 2017 covering 2829 patients treated with EVLA of the GSV. The success rates ranged from 77% to 100%, with a pooled success rate of 92% (95% CI 90%–94%). At univariable and multivariable meta-regression analyses, treatment success rates were not signicantly affected by wavelength, administered energy, or length of follow-up. In particular, there was no statistically signicant dif­ference between follow-up groups at 1 year, 1–3 years, and >3 years (93% [95% CI 87%–97%], 93% [95% CI 90%–95%], and 90% [95% CI 83%–94%], respectively, p = 0.82).