5 August 2014 Thulium fiber laser ablation of kidney stones using a 50-μm-core silica optical fiber
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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.
© 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)
Richard L. Blackmon, Thomas C. Hutchens, Luke A. Hardy, Christopher R. Wilson, Pierce B. Irby, Nathaniel M. Fried, "Thulium fiber laser ablation of kidney stones using a 50-μm-core silica optical fiber," Optical Engineering 54(1), 011004 (5 August 2014). https://doi.org/10.1117/1.OE.54.1.011004

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