Ho:YAG laser lithotripsy in non-contact mode: optimization of fiber to stone working distance to improve ablation efficiency
To evaluate how variable working distances between the laser fiber and the stone influence ablation volume.
A laser fiber was fixed on a robotic arm perpendicular to an artificial stone. A single laser pulse was triggered at different working distances (0–2.0 mm in 0.2 mm increments) between the distal fiber tip and the stone. To achieve a measurable impact, pulse energy was set to 2 and 3 J, with either short or long pulse duration. Ablation volume was calculated with an optical microscope. Experiments were repeated five times for each setting.
Highest ablation volume was observed with a long pulse of 3 J at a working distance of 0.4 mm between the laser fiber and the stone surface (p value < 0.05). At 2 J, the highest ablation volume was noticed with a short pulse in contact mode. However, ablation volume of the latter was not significantly greater than with a long pulse of 2 J at a working distance of 0.4 mm (p value > 0.05). Compared to lithotripsy in contact mode, triggering a single long pulse at 0.4 mm increased ablation volume by 81% (p value = 0.016) at 2 J and by 89% (p value = 0.034) at 3 J.
For Ho:YAG laser lithotripsy, ablation volume may be higher in non-contact mode using long pulses, rather than in direct contact to the stone. Findings of the current study support the need of further studies of lithotripsy in non-contact mode.
KeywordsDistance Ho:YAG Laser Nephrolithiasis Non-contact
We would like to express our greatest appreciation to Prof. Gregory Altshuler, Prof. Nathaniel M. Fried and Viktoriya Vinnichenko for their valuable suggestions and proofreading of this article.
VDC: protocol/project development, data collection or management, data analysis, manuscript writing/editing. EXK: protocol/project development, data collection or management, data analysis, manuscript writing/editing. PC: protocol/project development, data collection or management, data analysis. LD: protocol/project development. EE: protocol/project development. SD: protocol/project development, data analysis. LB: protocol/project development, data analysis. OT: protocol/project development, data collection or management, data analysis, manuscript writing/editing.
Prof. Olivier Traxer is a consultant for Coloplast, Rocamed, Olympus, EMS and Boston Scientific. Dr. Steeve Doizi is a consultant for Coloplast. Dr. Vincent De Coninck is supported by the EUSP scholarship from the European Association of Urology and by a grant from the Belgische Vereniging voor Urologie (BVU). Dr. Etienne Xavier Keller is supported by a Travel Grant from the University Hospital Zurich and by a grant from the Kurt and Senta Herrmann Foundation.
Compliance with ethical standards
We did not perform research involving human participants and/or animals.
Supplementary material 1 (MP4 1604 KB)
Supplementary material 2 (MP4 1890 KB)