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Journal of Biomedical Optics

Miniature ball-tip optical fibers for use in thulium fiber laser ablation of kidney stones
Author(s): Christopher R. Wilson; Luke A. Hardy; Joshua D. Kennedy; Pierce B. Irby; Nathaniel M. Fried
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Paper Abstract

Optical fibers, consisting of 240-μm-core trunk fibers with rounded, 450-μm-diameter ball tips, are currently used during Holmium:YAG laser lithotripsy to reduce mechanical damage to the inner lining of the ureteroscope working channel during fiber insertion and prolong ureteroscope lifetime. Similarly, this study tests a smaller, 100-μm-core fiber with 300-μm-diameter ball tip during thulium fiber laser (TFL) lithotripsy. TFL was operated at a wavelength of 1908 nm, with 35-mJ pulse energy, 500-μs pulse duration, and 300-Hz pulse rate. Calcium oxalate/phosphate stone samples were weighed, laser procedure times were measured, and ablation rates were calculated for ball tip fibers, with comparison to bare tip fibers. Photographs of ball tips were taken before and after each procedure to track ball tip degradation and determine number of procedures completed before need for replacement. A high speed camera also recorded the cavitation bubble dynamics during TFL lithotripsy. Additionally, saline irrigation rates and ureteroscope deflection were measured with and without the presence of TFL fiber. There was no statistical difference (P>0.05) between stone ablation rates for single-use ball tip fiber (1.3±0.4  mg/s) (n=10), multiple-use ball tip fiber (1.3±0.5  mg/s) (n=44), and conventional single-use bare tip fibers (1.3±0.2  mg/s) (n=10). Ball tip durability varied widely, but fibers averaged greater than four stone procedures before failure, defined by rapid decline in stone ablation rates. Mechanical damage at the front surface of the ball tip was the limiting factor in fiber lifetime. The small fiber diameter did not significantly impact ureteroscope deflection or saline flow rates. The miniature ball tip fiber may provide a cost-effective design for safe fiber insertion through the ureteroscope working channel and into the ureter without risk of instrument damage or tissue perforation, and without compromising stone ablation efficiency during TFL lithotripsy.

Paper Details

Date Published: 19 January 2016
PDF: 8 pages
J. Biomed. Opt. 21(1) 018003 doi: 10.1117/1.JBO.21.1.018003
Published in: Journal of Biomedical Optics Volume 21, Issue 1
Show Author Affiliations
Christopher R. Wilson, The Univ. of North Carolina at Charlotte (United States)
Luke A. Hardy, The Univ. of North Carolina at Charlotte (United States)
Joshua D. Kennedy, 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)


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