Category: Clinical Stones: Ureteroscopy

MP24-5 - Ho:YAG laser lithotripsy in non-contact mode: optimization of fiber to stone working distance to improve ablation efficiency

Sun, Sep 23
10:00 AM - 12:00 PM

Introduction & Objective :

It is assumed that laser lithotripsy is most efficient in contact mode. We aimed to evaluate how a variable working distance between the laser fiber and the stone influences lithotripsy efficiency.


Methods :

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 to 2.0mm in 0.2mm increments) between the distal fiber tip and the stone. Pulse energy was set to 2 and 3J, with either short or long pulse duration. Ablation volume was calculated with an optical microscope. Experiments were repeated five times for each setting.


Results :

Highest ablation volume was observed with a long pulse of 3J at a working distance of 0.4mm between the laser fiber and the stone surface (p-value 0.05). At 2J, 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 0.4mm (p-value>0.05). Compared to lithotripsy in contact mode, triggering a single long pulse at 0.4mm increased ablation volume by 81% (p-value=0.016) at 2J and by 89% (p-value=0.034) at 3J.


Conclusions :

For Ho:YAG laser, highest efficiency may be achieved with high energy and long pulses at a working distance of 0.4mm between laser fiber tip and the stone surface, rather than in direct contact to the stone. Findings of the current study support the need of further studies of non-contact laser lithotripsy.

Vincent De Coninck

Urologist
AZ Klina
Brasschaat, Antwerpen, Belgium

Vincent De Coninck graduated as a medical doctor from the Free University of Brussels, Belgium (VUB) in 2011. He became a certified urologist in 2017 after a training at the University Hospital of Brussels (Prof. Dr. Dirk Michielsen) and OLV Aalst (Prof. Dr. Alex Mottrie), where he developed a special interest in the minimal invasive treatment of benign and malignant pathologies. In the same year, he became Fellow of the European Board of Urology.
In 2018, he completed a one-year fellowship program of the Endourological Society in Paris, France under the supervision of Prof. Dr. Olivier Traxer. During that fellowship, he also obtained a diploma in urolithiasis, organized by Dr. Michel Daudon at the Sorbonne University in Paris, France. Afterwards, he was trained in HoLEP by Dr. Karin Lehrich in Berlin, Germany.
Currently, he is completing a three-month fellowship under the supervision of Dr. Guido Giusti in Milan, Italy. In December 2018, he will start working as an endourologist in AZ Klina, Brasschaat, Belgium. He will focus on the medical and surgical treatment of kidney stones and benign prostatic obstruction (HoLEP) and he will continue publishing articles relating to the management of patients with renal stone disease.

Etienne X. Keller

Fellow of the ES
Sorbonne Université, GRC n°20, Groupe de Recherche Clinique sur la Lithiase Urinaire, AP-HP, Hôpital Tenon, F-75020 Paris, France
Paris, Ile-de-France, France

Paul H.L. Chiron

MD, FEBU
Sorbonne Université, GRC n°20, Groupe de Recherche Clinique sur la Lithiase Urinaire, AP-HP, Hôpital Tenon, F-75020 Paris, France
Saint Mandé, Ile-de-France, France

Laurian B. Dragos

Consultant Urologist
University of Medicine and Pharmacy Victor Babes, Timisoara, Romania
Timisoara, Timis, Romania

Steeve S. Doizi

Urologist
Sorbonne Université, GRC n°20, Groupe de Recherche Clinique sur la Lithiase Urinaire, AP-HP, Hôpital Tenon, F-75020 Paris, France
Paris, Ile-de-France, France

Laurent L. Berthe

Paris, Ile-de-France, France

Olivier O. Traxer

Professor
Sorbonne Universite, GRC n020 Lithiase Renale, AP-HP, Hospital Tenon, F-75020 Paris, France
Paris, Ile-de-France, France