The Thulium fiber laser (TFL) is being explored as an alternative to Holmium:YAG laser for lithotripsy. TFL beam
profile allows coupling of higher power into smaller fibers than multimode Holmium laser beam, without proximal
fiber tip degradation. A smaller fiber provides more space in ureteroscope working channel for increased saline
irrigation and allows maximum ureteroscope flexion. However, distal fiber tip burnback increases as fiber diameter
decreases. Previous studies utilizing hollow steel sheaths around recessed distal fiber tips reduced fiber burnback,
but increased retropulsion. In this study, a “fiber muzzle brake” was tested for reducing fiber burnback and stone
retropulsion. TFL lithotripsy studies were performed at 1908 nm, 35 mJ, 500 μs, and 300 Hz using a 100-μm-core
fiber. The optimal stainless steel muzzle brake tip tested consisted of a 1-cm-long, 560-μm-OD, 360-μm-ID tube
with 275-μm thru hole located 250-μm from the distal end. The fiber tip was recessed a distance of 500 μm. Stone
phantom retropulsion, fiber tip burnback, and calcium oxalate stone ablation studies were performed, ex vivo. Small
stones with a mass of 40 ± 4 mg and 4-mm-diameter were ablated over a 1.5-mm sieve in 25 ± 4 s (n=10), without
distal fiber tip burnback. Reduction in stone phantom retropulsion distance by 50% and 85% was observed when
using muzzle brake tips versus 100-μm-core bare fibers and hollow steel tip fibers. The muzzle brake fiber tip
provided efficient stone ablation, reduced stone retropulsion, and minimal fiber degradation during TFL lithotripsy.
Thomas C. Hutchens, David A. Gonzalez, Pierce B. Irby, and Nathaniel M. Fried, "Thulium fiber laser lithotripsy using a muzzle brake fiber tip," Proc. SPIE 10038, Therapeutics and Diagnostics in Urology: Lasers, Robotics, Minimally Invasive, and Advanced Biomedical Devices, 100380G (Presented at SPIE BiOS: January 29, 2017; Published: 6 February 2017); https://doi.org/10.1117/12.2250994.
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