Thulium:YAG laser: a good compromise between holmium:YAG and thulium fiber laser for endoscopic lithotripsy? A narrative review

Abstract

Purpose: To provide a technological description of the new pulsed solid-state Thulium:YAG laser (Tm:YAG). In addition, current available literature on Tm:YAG lithotripsy is also reviewed.

Materials and methods: Medline, Scopus, Embase, and Web of Science databases were used to search for Tm:YAG operating mode articles.

Results: Tm:YAG technology works with a laser cavity with thulium-doped YAG crystal, pumped by laser diodes. Laser beam operates at 2013 nm, with an adjustable peak power (≥ 1000 W) and the minimal fiber laser diameter is of 200 µm. It has an intermediate water absorption coefficient and peak power-pulse duration. Various pulse modulations are proposed, aiming to minimize stone retropulsion. Multiple comparative in vitro studies suggest that Tm:YAG's ability to fragment stones is similar to the one of the Ho:YAG laser; on the contrary, its ability to dust all stone types is similar to the one of the TFL, with a low retropulsion. A single in vivo study assessed Tm:YAG lithotripsy feasibility.

Conclusions: The new pulsed solid-state thulium:YAG laser could represent a safe and effective compromise between Ho:YAG laser and TFL for endoscopic lithotripsy, either in retrograde intra-renal surgeries or in percutaneous nephrolithotomy.

Keywords: Holmium:YAG; Laser; Lithotripsy; Thulium YAG; Thulium fiber laser; Ureteroscopy.