Moses™ technology has been developed to improve holmium laser fragmentation at 1-2 mm distance from the stone. Because popcorn lithotripsy is a non-contact technique, we compared short pulse (SP) and Moses distance (MD) modes in an in vitro model.
BegoStones were fragmented using a 120 W Ho:YAG laser (P120 Moses) and a 230 μm core fiber introduced through a ureteroscope. 20 W (1 J × 20 Hz; 0.5 J × 40 Hz) and 40 W (1 J × 40 Hz; 0.5 J × 80 Hz) settings (total energy 4.8 kJ) were tested using SP and MD modes. We assessed fragment size distribution and mass lost in fluid (initial mass-final dry mass of all sievable fragments). High-speed video analysis of fragmentation strike rate and vapor bubble characteristics was conducted for 1 J × 20 Hz and 0.5 J × 80 Hz. Laser strike rate (number of strikes divided by frequency) was categorized as: (1) direct-a visual plume of dust ejected from stone while in contact with fiber tip; (2) indirect-a visual plume of dust ejected with distance between stone and fiber tip.
For 1 J × 20 Hz (20 W), MD resulted in more mass lost in fluid and a lower distribution of fragments ≥ 2 mm compared to SP (p < 0.05). 0.5 J × 80 Hz (40 W) produced no fragments ≥ 2 mm, and there were no significant differences in fragment distribution between MD and SP (p = 0.34). When using MD at 1 J × 20 Hz, 96% of strikes were indirect vs 61% for SP (p = 0.059). In contrast to the single bubble of SP, with MD, there was forward movement of the collapsing second bubble, away from the fiber-tip.
For lower frequency and power popcorn settings, pulse modulation results in more fragmentation through true non-contact laser lithotripsy.
World journal of urology. 2020 Jun 06 [Epub ahead of print]
Kristian M Black, Ali H Aldoukhi, Joel M H Teichman, Sami E Majdalany, Timothy L Hall, William W Roberts, Khurshid R Ghani
Medical Sciences Unit I, Division of Endourology, Department of Urology, University of Michigan, 1301 Catherine St, Room 4432, Ann Arbor, MI, 48109, USA. ., Medical Sciences Unit I, Division of Endourology, Department of Urology, University of Michigan, 1301 Catherine St, Room 4432, Ann Arbor, MI, 48109, USA., Department of Urologic Sciences, University of British Columbia, Vancouver, BC, Canada., Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.