Pulsed CO₂ laser beam delivery and real time temperature measurements via silver-halide fiber into biological in-vitro samples: Hystological analysis and internal temperature distributions calculation

The morphometrical analysis of the effect of a pulsed CO₂ laser on in vitro fresh rabbit vessel tissue was performed. The laser energy was delivered through a silver-halide fiber and the real time temperature was monitored via a second silver-halide fiber positioned on the external side of the irradiated tissue sample. In addition. a mathematical model was identified and applied on the analysis of the samples to quantify the internal temperature distribution. The model takes into account the dimension (coagulation. vacuolization) and the speed of the receding boundaiy between the ablated and normal tissue in a pulsed beam mode. Superficial hystological lesions were observed with ranges of energies of 20 msec/pulse. 1 Hz. 2 Hz. at 100 mJ. corresponding to a measured maximal external temperature range between 500 and f()0 C. The used mathematical model has shoi good agreement with these experimentally collected temperature measurements. Higher repetition rates for both 33 and 100 mi/p were found to produce crater formation. in all the samples. The correspondent measured external temperatures were between 55°and 950 C and the calculated internal temperature of the injured layers were 142-306° C. corresponding to the carbonization zones and depending on the type of tissue. The morphometrical analysis have shown: The Co2 laser effect on the tissue is dependent on the angle of irradiapon.The stereo metrical configuration and the water content of the irradiated tissue. A threshold value for injury generation is proposed.