How to perform the dusting technique for calcium oxalate stone phantoms during Ho:YAG laser lithotripsy

Abstract

Background: To determine the most efficacious setting of Holmium:yttrium-aluminum-garnet (Ho:YAG) laser with a maximum power output of 120 W with in vitro phantom-stone dusting technique.

Methods: A laser was used to treat two 4 × 3 × 3 mm³ sized phantom stones in 5 mL syringes with 1 mm-sized holes at the bottom. According to the pulse width (short 500, middle 750, long pulse 1000 μsec), maximal pulse repetition rates from 50 to 80 Hz were tested with pulse energy of 0.2, 0.4, 0.5, and 0.8 J. Six times of the mean dusting times were measured at each setting. Dusting was performed at continuous firing of the laser until the stones become dusts < 1 mm.

Results: The mean Hounsfield unit of phantom stones was 1309.0 ± 60.8. The laser with long pulse generally showed shorter dusting times than short or middle pulse width. With increasing the pulse energy to 0.5 J, the dusting time decreased. However, the pulse energy of 0.8 J showed longer dusting times than those of 0.5 J. On the post-hoc analysis, the pulse energy of 0.5 J, long pulse width, and the repetition rates of 70 Hz demonstrated significantly shorter dusting times than other settings.

Conclusions: The results suggest that long pulse width with 0.5 J and 70 Hz would be the most efficacious setting for dusting techniques of plaster stone phantoms simulating calcium oxalate stones using the 120 W Ho:YAG laser.

Keywords: Calcium oxalate; Dusting; Energy; Ho:YAG laser; Lithotripsy.

Fig. 1

a Stone density measured in the computed tomography scan images. b Each cubical stone of 4x3x3 mm³

Fig. 2

a A 1 mm-sized hole at the bottom of the syringe for fragmented particles to go out. b A laser fiber was positioned 1–2 mm away from the phantom stones when the dusting technique starts. c Irrigation fluid at the height of 40cmH₂O to mimic the real practice situation. d Dusts < 1 mm went out of the syringe during laser firing. When the all particles disappear in the syringe, the duration of dusting was checked by a stop-watch

Fig. 3

Post-hoc analysis to compare the mean dusting time per each setting and across the groups a (0.5 J, a long pulse width, and 70 Hz), b (0.5 J (middle and short pulse widths), c (0.4 and 0.8 J, middle or short pulse width), and d (0.2 J groups)