In vitro evaluation of the new holmium:yttrium-aluminium-garnet laser with Magneto technology on behalf of the Progress and Collaboration in Endourology (PACE) group.

OBJECTIVES

To evaluate the following characteristics of the holmium:yttrium-aluminium-garnet (Ho:YAG) laser with Magneto technology: pulse shape, shape and duration of the laser-induced vapour bubble (VB), power loss over time, and the risk of fibre fracture (RFF).

METHODS

A 150 W Ho:YAG generator was characterised in vitro with Magneto technology. The pulse shape was measured using an oscilloscope. The pulse duration was measured to calculate the peak power (PP) using both a 200- and 550-μm laser fibre (LF). VB were evaluated with a 200-μm fibre using a high-speed camera (8000 frames/s). Power loss over time was obtained at the fibre tip before and after 30 s, then 1 min of continuous laser activation in saline solution and in contact with BegoStone® (BEGO GmbH & Co., Bremen, Germany). Power loss was evaluated using LFs with core diameters of 200, 365, and 550 μm. RFF was tested after 5 min of continuous laser activation or until LF fracture with different laser settings and LF bending radii (0.45, 0.6, 0.9 cm) using a 200-μm LF.

RESULTS

The Ho:YAG laser with the Magneto technology possesses a quasi-rectangular waveform with extended pulse durations ranging between 0.7 and 1.7 ms and limited PPs between a mean (standard deviation) of 513.4 (23.3) to 1149.7 (6.9) W that increase proportionally with power. However, multiple spikes were observed within each pulse, precluding a perfectly linear plateau. Regarding VB, it was significantly wider with the 550-μm LF compared to the 200-μm LF. Conversely, the VB duration was significantly longer with the 200-μm LF. A consistent initial power loss was observed in normal saline of 13-28.0% across all LF diameters, which progressed during continuous activation of up to 1 min. This power degradation was more pronounced on synthetic BegoStone. No LF fractures were observed under the tested experimental conditions.

CONCLUSION

The new Ho:YAG laser with Magneto technology appears to be a promising compromise between conventional Ho:YAG and thulium fibre laser, owing to its pulse profile with a limited PP.