Fluorescence-Guided Laser Lithotripsy: First Experience From a Clinical Study With Automatic Blocking of the Treatment Laser Beam

For several years, research has been conducted into fluorescence-controlled laser lithotripsy, with the aim of preventing tissue and material damage in the event of incorrect fiber positioning. Here, the lithotripsy laser is only released into the treatment fiber if the fluorescence signal of the stone, excited via the fiber using a pilot laser, exceeds a predetermined threshold value. We have explored the clinical usability of such a system. Triggering of the holmium laser by the physician and its automatic blocking (shutter open/closed) were recorded in addition to the fluorescence signal. Visual comparison with the image data from the ureteroscope allowed us to evaluate limitations of the method and assess its effectiveness. The laser was used at a pulse rate of 6 Hz and a pulse energy of 0.6–1.6 J for four interventions (three ureteral stones and one stent encrustation). The lasing time ranged from 29 to 342 s. During the fragmentation of the ureteral stones, 1119 in the removal of the encrustation, 58 subjective assessment of 60 pulse trains (time period in which the laser is continuously triggered), pulses that would have contributed to ablation were blocked in 8 pulse trains in the case of the stent encrustation, but only in one pulse train in the case of the urinary calculi. In the urinary stone interventions, pulses were not blocked in seven cases where the fiber was close to tissue or on material (stent, wire). Overall, the system could be used within the framework of our study without any problems. In the case of ureteral stones, surgeons did not perceive any restriction due to the feedback control.