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Journal of Biomedical Optics

Thulium fiber laser lithotripsy in an in vitro ureter model
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Paper Abstract

Using a validated in vitro ureter model for laser lithotripsy, the performance of an experimental thulium fiber laser (TFL) was studied and compared to the clinical gold standard holmium:YAG laser. The holmium laser (λ=2120  nm) was operated with standard parameters of 600 mJ, 350  μs, 6 Hz, and 270-μm-core optical fiber. The TFL (λ=1908  nm) was operated with 35 mJ, 500  μs, 150 to 500 Hz, and a 100-μm-core fiber. Urinary stones (60% calcium oxalate monohydrate/40% calcium phosphate) of uniform mass and diameter (4 to 5 mm) were laser ablated with fibers through a flexible video-ureteroscope under saline irrigation with flow rates of 22.7 and 13.7  ml/min for the TFL and holmium laser, respectively. The temperature 3 mm from the tube’s center and 1 mm above the mesh sieve was measured by a thermocouple and recorded throughout each experiment for both lasers. Total laser and operation times were recorded once all stone fragments passed through a 1.5-mm sieve. The holmium laser time measured 167±41  s (n=12). TFL times measured 111±49, 39±11, and 23±4  s, for pulse rates of 150, 300, and 500 Hz, respectively (n=12 each). Mean peak saline irrigation temperatures reached 24±1°C for holmium, and 33±3°C, 33±7°C, and 39±6°C, for TFL at pulse rates of 150, 300, and 500 Hz, respectively. To avoid thermal buildup and provide a sufficient safety margin, TFL lithotripsy should be performed with pulse rates below 500 Hz and/or increased saline irrigation rates. The TFL rapidly fragmented kidney stones due in part to its high pulse rate, high power density, high average power, and observation of reduced stone retropulsion and may provide a clinical alternative to the conventional holmium laser for lithotripsy.

Paper Details

Date Published: 16 December 2014
PDF: 6 pages
J. Biomed. Opt. 19(12) 128001 doi: 10.1117/1.JBO.19.12.128001
Published in: Journal of Biomedical Optics Volume 19, Issue 12
Show Author Affiliations
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 Medical Institutions (United States)

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