Retropulsion force in laser lithotripsy—an in vitro study comparing a Holmium device to a novel pulsed solid-state Thulium laser

Abstract

Purpose To investigate retropulsion forces generated by two laser lithotripsy devices, a standard Ho:YAG and a new pulsed solid-state Thulium laser device. Materials and methods Two different Dornier laser devices were assessed: a Medilas H Solvo 35 and a pulsed solid-state Thulium laser evaluation model (Dornier MedTech Laser GmbH, Wessling, Germany). We used a 37 °C water bath; temperature was monitored with a thermocouple/data-logger. Representative sets of settings were examined for both devices, including short and long pulse lengths where applicable. For each setting, ten force values were recorded by a low-force precision piezo sensor whereby the laser fibre was either brought into contact with the sensor or placed at a 3 mm distance. Results The mean retropulsion forces resulting from the new Tm:YAG device were significantly lower than those of the Ho:YAG device under all pulse energy and frequency settings, ranging between 0.92 and 19.60 N for Thulium and 8.09–39.67 N for Holmium. The contact setups yielded lower forces than the distance setups. The forces increased with increasing pulse energy settings while shorter pulse lengths led to 12–44% higher retropulsive force in the 2.0 J/5 Hz comparisons. Conclusion The Tm:YAG device not only significantly generated lower retropulsion forces in all comparisons to Holmium at corresponding settings but also offers adjustment options to achieve lower energy pulses and longer pulse durations to produce even lower retropulsion. These advantages are a promising add-on to laser lithotripsy procedures and may be highly relevant for improving laser lithotripsy performance.

Thulium fibre laser vs holmium: yttrium‐aluminium‐garnet laser lithotripsy for urolithiasis: meta‐analysis of clinical studies

“…This was also consistent with the preclinical study reported by Petzold et al. [38], which illustrated that compared to the Holmium:YAG laser, the TFL was able to render faster stone ablation and lower retropulsion.…”

“…Furthermore, when treating ureteric stones using URS with better pulse control, the degree of retropulsion was significantly lesser for TFL compared to Ho:YAG without a MOSES setting. This was also consistent with the preclinical study reported by Petzold et al [38], which illustrated that compared to the Holmium:YAG laser, the TFL was able to render faster stone ablation and lower retropulsion.…”

Transient pressure field measurement of Ho:YAG laser in water

“…The Ho:YAG laser has been the favored lithotripter for the treatment of urinary calculus since shortly after its introduction in the 1990s [1][2] because it can fragment all calculus compositions and produces less calculus migration (retropulsion) during treatment than the short-pulsed lasers [3]. Although the lamp-pumped Ho:YAG laser has been commercialized for ureteroscopic laser lithotripsy (URS) for almost 25 years, a commercially available Ho:YAG laser delivers large energy and short pulses that generate omnidirectional vapor bubbles, wasting a significant percentage of the input energy [4][5][6][7][8]. The Smart Modes of the prototype laser generate narrowly focused vapor bubbles that travel forward greater distances and deliver more energy to the target calculus.…”

Can We Identify Patients in Danger of Complications in Retrograde Intrarenal Surgery?—A Retrospective Risk Factors Analysis

“…A different laser incorporating this chemical element is Thulium: Yttrium-Aluminium-Garnet, however still being under investigation. This technology generates 120 W power, energy 0.1-3 J, and high frequency impulses up to 200 Hz, yet promises a low retropulsion effect due to long energy impulses [21,22].…”