In-vitro studies investigating the stone-fragmenting parameters of the multi-YAG laser

The multi-YAG laser is a multi-purpose surgical laser designed with the ability to emit 1440 nm light in the pulsed mode for ablation of tissue. Preliminary studies have shown that this laser can rapidly ablate urinary calculi. To define the optimal parameters for laser lithotripsy, 60 uric acid (UA) stones and 60 calcium oxalate monohydrate (COM) stones were ablated in a controlled in vitro study. Each stone was fragmented to less than 1.5 mm while varying the pulse energy (0.3 J to 1.5 J) and the pulse frequency (5 Hz to 15 Hz). The mean energy required to fragment a milligram of stone (fragmentation efficacy - J/mg) was calculated for each experimental level and then compared. The pulse frequency did not significantly affect the fragmentation efficacy for the UA stones (p equals 0.4069) or the COM stones (p equals 0.2560) but, it was significantly affected by the pulse energy for both groups (p less than 0.001). In addition, a plateau in the fragmentation efficacy occurred for both stone groups with respect to the pulse energy. For the UA stones, there was no improvement in the efficacy of fragmentation beyond 0.3 J/pulse and for the COM stones, this plateau did not occur until 0.9 J/pulse. Overall, the COM stones required more energy for fragmentation (p equals 0.001), but efficient and rapid ablation was achieved at energies between 0.6 J and 0.9 J/pulse. These results suggest that the multi-YAG laser has the ability to efficiently ablate urinary calculi of variable composition.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.