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Online ISSN 1827-1766
Passariello F., Goldman M. P., Mordon S., Corcos L., Vaghi M., Gonzales Zeh R.
Centro Diagnostico Aquarius , Napoli
The study of the mechanism of action on biological tissues is useful to clarify the device configuration parameters which can influence the biological effect. This report summarizes the Internet discussion on the mechanism of action of thermal ablation with laser or radiofrequency, and represents the collective work of the Laser-Floating Group. The Vasculab group supported the Internet discussion. RF heats the intimal layer by direct contact, inducing vein wall endothelial damage. Tumescent anaesthesia acts as an external heat sink to protect perivenous tissues. The scattering phenomenon affects „where“ the absorption will occur, usually reducing the penetration of light into the tissue. Heating decreases with tissue depth as absorption and scattering attenuate the incident beam. Based on the absorption and effective scattering coefficients of the biological tissue, the optical extinction coefficient can be computed for each laser wavelengths. According to simulation on models the classification of lasers into haemoglobin and water-specific wavelengths must be regarded as inappropriate. On the contrary, some data witness for a more gentle heating of the vein wall when using a 1320 nm Nd YAG laser, which has water rather than haemoglobin as target. Data are discordant also about the greater effect of the position of the fiber inside the vessel, centered or near the wall. Mordon reports that other new high wavelength diode lasers are actually in test. In conclusion, this review shows that much has still to be done in the field of basic research regarding the mechanism of biological action of endovenous lasers.