fotothermolyse

Fotothermolyse, or photothermolysis, is a process by which selected biological tissue is damaged or destroyed through the localized conversion of light energy into heat. The method relies on the presence of a chromophore—such as melanin in pigment, oxyhemoglobin in blood, or water in tissue—that strongly absorbs light at a chosen wavelength. When light is absorbed, energy is converted to heat, raising the temperature of the targeted structure and causing cellular coagulation, vaporization, or disruption, while surrounding tissue remains comparatively unharmed.

Principle and parameters: The technique is based on selective photothermolysis, which requires matching the light wavelength to the chromophore's absorption spectrum and selecting pulse duration and energy so that heat remains confined to the target within its thermal relaxation time. In practice, lasers (for example Nd:YAG, alexandrite, CO2, diode) and broad-spectrum light sources (intense pulsed light) are used. Short pulses deliver the energy rapidly, promoting precise targeting and reducing collateral damage.

Applications: In medicine, fotothermolyse is widely used in dermatology for pigmentary disorders, hair removal, and vascular lesions; examples include pigment lesions treated with Q-switched lasers, hair via diode lasers, and facial telangiectasias via pulsed-dye lasers or KTP. Outside dermatology, photothermal therapy explores heat-induced tumor ablation using light-absorbing agents such as nanoparticles.

Safety and considerations: Potential risks include burns, scarring, pigmentary changes, and infection; outcomes depend on skin type, device, and operator expertise. The concept was developed in the context of laser medicine in the late 20th century and remains central to modern light-based therapies.