Evaluation of thermal damage area of tissue around pulsed laser-induced bubbles in URS treatment based on CEM43

The pulsed laser used in URS (ureteroscopy) is used effectively in the treatment of urologic diseases such as lithotripsy and benign prostatic hyperplasia. In the case of lithotripsy in a relatively narrow area or prostatectomy, since it is necessary to irradiate the laser near or directly into the tissue through an optical fiber, it is pointed out that thermal damage may be caused to areas other than the affected area. The authors have measured the temperature near the fiber tip and attempted to evaluate the damage to biological tissues using an evaluation method called CEM43℃ (cumulative equivalent minutes at 43℃). In this report, we measured the time-averaged temperature distribution on the wall surface around the bubbles using thermocouples flush-mounted on the wall, and examined the range where the tissue wall is expected to be damaged using CEM43℃. As a result, we found that the possibility of thermal damage could occur in the area in front of the fiber tip. In addition, the thermal damage area is closely related to the contact between the bubbles and the wall surface associated with the characteristic collapse behavior of the bubbles formed near the wall surface.