Abstract
In general, laser surgery is based upon precise tissue heating when optical energy is absorbed within the skin, creating heat exactly where light is absorbed by molecules called chromophores. The major chromophores for visible and near-infrared light are melanin and hemoglobins while water and lipids are major mid- and far-infrared chromophores. Wavelength(s) of lasers or intense pulsed light (IPL) sources are often matched for absorption by chromophores in skin targets such as blood vessels, hair follicles, melanin-containing cells, tattoo ink, or tissue layers. Selective heating and damage of targets can occur when a pulse of selectively absorbed light or other energy is delivered faster than the targets can cool by heat conduction. The time for a tissue target to cool is its thermal relaxation time, equal in seconds to approximately the square of the target size in millimeters. Very short (nanosecond or picosecond) laser pulses, produced by Q-switched lasers, can precisely damage small targets such as individual melanocytes or nanoparticles. Millisecond laser and IPL pulses can selectively affect multicellular targets such as blood vessels, hair follicles, and tissue layers. In fractional laser treatments, an array of microscopic thermal injury zones is created. Additional energy technologies include radiofrequency or pulsed electrical current; high-intensity, focused ultrasound; and tissue cooling.
Published Version
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