Endoscopic assisted stone fragmentation

Abstract

Different clinically available pulsed laser systems emitting either in the IR- or VIS- spectral region were compared with respect to their impact on phantom stones and clinical calculi in a standardized manner. Furthermore the impact of laser radiation on the medical equipment was instigated.

Light of the pulsed laser systems emitting IR- (λ=2100nm: Ho:YAG-laser) or VIS- (λ=532nm/1064nm: FREDDY^®-laser; 598nm: FLPD-laser) light were used. The ablation threshold as well as the fragmentation rate and the sputtering rate of artificial and human calculi (urologic and salivary) of different compositions were measured and different fragmentation rates in relation to the fluence were calculated. In the same manner different equipment devices were tested. In order to underline the different primary laser induced processes that lead to fragmentation the generated shockwave pressures of the different laser devices were measured.

The ablation threshold value of IR-lasers was overstepped by the lowest laser setting independent to repetition rate and fibre diameter. There was no difference in the fragmentation and sputtering rate between different IR-lasers neither for stone phantoms nor for clinical stones. On stone phantoms VIS-lasers showed a 20 times higher fragmentation rate and a 10 times higher sputtering rate than the IR-lasers. All kinds of clinical calculi could be destroyed IR-lasers in contrast to using VIS-lasers. Equipment destruction could be induced by each laser.

Investigations on phantom stone fragmentation are useful to compare clinical laser parameter settings but can partially be transferred to clinical stone fragmentation. IR-lasers can induce ablation and fragmentation to all examined human calculi at lowest energy settings in contrast to VIS-lasers which could not induce ablation on some stone composites. The VIS-lasers are solely useful for laser induced shock wave lithotripsy while the IR-lasers are in use for other clinical applications (e.g. coagulation, ablation).