OBJECTIVE

To study thermal and transport processes during endovenous laser obliteration.

MATERIAL AND METHODS

We analyzed thermal and transport processes following water and blood boiling under continuous near infrared laser radiation (1.94 μm; 1.47 μm). Analysis was carried out in an experiment with non-deaerated water and during clinical procedure of endovenous laser obliteration. We applied high-speed video recording, acoustic and ultrasound methods. Endovenous blood boiling was intraoperatively assessed using a linear ultrasound transducer. Thermal obliteration was carried out using a 1.47 μm diode laser. In physical experiment, was applied a high-speed video camera (frame rate 10⁵ frames per second), 1.94 μm semiconductor laser and 400 μm quartz-quartz-polymer fibers. Broadband acoustic signals generated during laser-induced liquid boiling was recorded using a broadband hydrophone and 1-mm needle hydrophone. Acoustic signals arising during endovenous laser obliteration were recorded using a video camera. This camera was also used for simultaneous recording of image from ultrasound scanner monitor.

RESULTS

Laser-induced boiling is accompanied by generation of heated submerged jets. Volumetric effervescence of blood during vapor bubble collapse is accompanied by pressure oscillations and shock waves. Patients and medical staff perceive these effects as claps. The nature of these acoustic signals was analyzed.

CONCLUSION

Laser-induced boiling followed by heated submerged jets is one of the main mechanisms leading to rapid heating and coagulation of vascular wall, primarily epithelium, and subsequent obliteration.