When treating ureteral calculi, retropulsion can be reduced by using a longer pulse width
without compromising fragmentation efficiency (from the studies by David S. Finley et al. and
Hyun Wook Kang et al.). In this study, a lab build Ho:YAG laser was used as the laser pulse
source, with pulse energy from 0.2J up to 3.0 J, and electrical pump pulse width from 150 us up
to 1000 us. The fiber used in the investigation is a 365 μm core diameter fiber, SureFlexTM,
Model S-LLF365. Plaster of Paris calculus phantoms were ablated at different energy levels (0.2,
0.5, 1, 2, 3J) and with different number of pulses (1, 3, 10) using different electrical pump pulse
width (333, 667, 1000 μs). The dynamics of the recoil action of a calculus phantom was
monitored using a high-speed camera with frame rate up to 1 million frame per second
(Photron Fastcam SA5); and the laser-induced craters were evaluated with a 3-D digital
microscope (Keyence VHX-900F). A design of experiment software (DesignExpert-10,
Minneapolis, MN, USA) is used in this study for the best fit of surface response on volume of
dusting and retropulsion amplitude. The numerical formulas for the response surfaces of
dusting speed and retropulsion amplitude are generated. More detailed investigation on the
optimal conditions for dusting of other kinds of stone samples and the fiber size effect will be
conducted as a future study.
Jian J. Zhang, Jonathan Rutherford, Metasebya Solomon, Brian Cheng, Jason R. Xuan, Jason Gong, Honggang Yu, Michael Xia, Xirong Yang, Thomas Hasenberg, and Sean Curran, "The study of laser pulse width on efficiency of Ho:YAG laser lithotripsy," Proc. SPIE 10038, Therapeutics and Diagnostics in Urology: Lasers, Robotics, Minimally Invasive, and Advanced Biomedical Devices, 100380H (Presented at SPIE BiOS: January 29, 2017; Published: 20 February 2017); https://doi.org/10.1117/12.2250665.
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