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Optical Engineering

Thulium fiber laser ablation of kidney stones using a 50-μm-core silica optical fiber
Author(s): Richard L. Blackmon; Thomas C. Hutchens; Luke A. Hardy; Christopher R. Wilson; Pierce B. Irby; Nathaniel M. Fried
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Paper Abstract

Our laboratory is currently studying the experimental thulium fiber laser (TFL) as a potential alternative laser lithotripter to the gold standard, clinical Holmium:YAG laser. We have previously demonstrated the efficient coupling of TFL energy into fibers as small as 100-μm-core-diameter without damage to the proximal end. Although smaller fibers have a greater tendency to degrade at the distal tip during lithotripsy, fiber diameters (≤200  μm) have been shown to increase the saline irrigation rates through the working channel of a flexible ureteroscope, to maximize the ureteroscope deflection, and to reduce the stone retropulsion during laser lithotripsy. In this study, a 50-μm-core-diameter, 85-μm-outer-diameter, low-OH silica fiber is characterized for TFL ablation of human calcium oxalate monohydrate urinary stones, ex vivo. The 50-μm-core fiber consumes approximately 30 times less cross-sectional area inside the single working channel of a ureteroscope than the standard 270-μm-core fiber currently used in the clinic. The ureteroscope working channel flow rate, including the 50-μm fiber, decreased by only 10% with no impairment of ureteroscope deflection. The fiber delivered up to 15.4±5.9  W under extreme bending (5-mm-radius) conditions. The stone ablation rate measured 70±22  μg/s for 35-mJ-pulse-energy, 500-μs-pulse-duration, and 50-Hz-pulse-rate. Stone retropulsion and fiber burnback averaged 201±336 and 3000±2600  μm, respectively, after 2 min. With further development, thulium fiber laser lithotripsy using ultra-small, 50-μm-core fibers may introduce new integration and miniaturization possibilities and potentially provide an alternative to conventional Holmium:YAG laser lithotripsy using larger fibers.

Paper Details

Date Published: 5 August 2014
PDF: 7 pages
Opt. Eng. 54(1) 011004 doi: 10.1117/1.OE.54.1.011004
Published in: Optical Engineering Volume 54, Issue 1
Show Author Affiliations
Richard L. Blackmon, The Univ. of North Carolina at Chapel Hill (United States)
Thomas C. Hutchens, The Univ. of North Carolina at Charlotte (United States)
Luke A. Hardy, The Univ. of North Carolina at Charlotte (United States)
Christopher R. Wilson, The Univ. of North Carolina at Charlotte (United States)
Pierce B. Irby, Carolinas Medical Ctr. (United States)
Nathaniel M. Fried, The Univ. of North Carolina at Charlotte (United States)
Carolinas Medical Ctr. (United States)
Johns Hopkins Univ. (United States)

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