Theoretical bases of calculation of energy parameters of laser radiation for thermotherapy of Baker's cyst.

Abstract

Actuality: Interstitial application of light energy to pathological tissues of small volume always raises concerns about the possible negative impact of excessive thermal effects on the surrounding unchanged structures. At the same time, insufficient thermal exposure does not allow achieving the desired result of manipulation. In particular, with a similar problem, there are surgeons performing laser-induced thermotherapy of cysts of different localization.
 Objective: Determine the time to reach the desired temperature required for the irreversible coagulation of the wall of the Baker cyst, depending on the power of the laser radiation and the volume of the intracystic fluid.
 Materials and methods: Several series of experiments were carried out in which different volumes of aqueous lidocaine solution were heated in disposable syringes by laser radiation fed along a flexible light-bearing fiber. Registration of infrared radiation from this system was performed by a portable thermal imager CONDTROL IR-CAM (Russia). The time for heating the syringe to 70 ° C was measured at different radiation powers.
 Results: In all series of experiments, a predetermined temperature of 70 ° C was achieved, providing instantaneous protein coagulation. Attention is drawn to the fact that the calculated time by the formula (ideal) in all cases is less, which can be explained by the effect of heat removal from the walls of syringes. The higher the power of laser radiation, the less the effect of heat removal on the heating rate of the aqueous solution, and, accordingly, the time to reach the set temperature.
 Conclusion. In the energy regimes and volumes of the aqueous solution studied, the optical fiber with end radiation emission is not capable of causing carbonization and damage to surrounding tissues. Accordingly, contactless perforation of the cyst wall by laser radiation with a wavelength of 1.47 μm is impossible. The obtained data testify to the advisability of calculating the energy to reach the set temperature and keeping it for a period sufficient for coagulation transformation of the more external layers of education