Upper Urinary Tract
In vitro fragmentation efficiency of holmium: yttrium-aluminum-garnet (YAG) laser lithotripsy – a comprehensive study encompassing different frequencies, pulse energies, total power levels and laser fibre diameters
Article first published online: 16 APR 2014
© 2013 The Authors. BJU International © 2013 BJU International
Volume 114, Issue 2, pages 261–267, August 2014
How to Cite
Kronenberg, P. and Traxer, O. (2014), In vitro fragmentation efficiency of holmium: yttrium-aluminum-garnet (YAG) laser lithotripsy – a comprehensive study encompassing different frequencies, pulse energies, total power levels and laser fibre diameters. BJU International, 114: 261–267. doi: 10.1111/bju.12567
- Issue published online: 28 JUL 2014
- Article first published online: 16 APR 2014
- Accepted manuscript online: 13 NOV 2013 05:39AM EST
- holmium:YAG laser lithotripsy;
- urinary calculi;
- high frequency lithotripsy;
- lithotripter settings;
- automated laser fragmentation testing system
To assess the fragmentation (ablation) efficiency of laser lithotripsy along a wide range of pulse energies, frequencies, power settings and different laser fibres, in particular to compare high- with low-frequency lithotripsy using a dynamic and innovative testing procedure free from any human interaction bias.
Materials and Methods
An automated laser fragmentation testing system was developed.
The unmoving laser fibres fired at the surface of an artificial stone while the stone was moved past at a constant velocity, thus creating a fissure.
The lithotripter settings were 0.2–1.2 J pulse energies, 5–40 Hz frequencies, 4–20 W power levels, and 200 and 550 μm core laser fibres.
Fissure width, depth, and volume were analysed and comparisons between laser settings, fibres and ablation rates were made.
Low frequency-high pulse energy (LoFr-HiPE) settings were (up to six times) more ablative than high frequency-low pulse energy (HiFr-LoPE) at the same power levels (P < 0.001), as they produced deeper (P < 0.01) and wider (P < 0.001) fissures.
There were linear correlations between pulse energy and fragmentation volume, fissure width, and fissure depth (all P < 0.001).
Total power did not correlate with fragmentation measurements.
Laser fibre diameter did not affect fragmentation volume (P = 0.81), except at very low pulse energies (0.2 J), where the large fibre was less efficient (P = 0.015).
At the same total power level, LoFr-HiPE lithotripsy was most efficient. Pulse energy was the key variable that drove fragmentation efficiency.
Attention must be paid to prevent the formation of time-consuming bulky debris and adapt the lithotripter settings to one's needs.
As fibre diameter did not affect fragmentation efficiency, small fibres are preferable due to better scope irrigation and manoeuvrability.