Monitoring of laser ablation of biotissues on backscattered radiation

The monitoring system for laser vaporization of biotissues based on autodyne detection method of backscattered radiation with the help of high-frequency pumping CO₂ laser was developed. It was shown that this method gives the possibility to determine the instant of laser beam passage through tissue layers boundary in real-time. The magnitudes of integrated intensity of power spectrum (UPS) and weighted mean frequency of Doppler signal spectrum (v) were used for the characterization of Doppler signal in time of laser pulse. As an example the dependencies of IIPS(t) and v(t) for different sets of tissue layers are presented. The stick-slip change of these magnitudes near tissue layers boundary is the base of feed-back for irradiation stopping and change of laser radiation parameters