Research Papers: Therapeutic

Thulium fiber laser lithotripsy in an in vitro ureter model

[+] Author Affiliations
Luke A. Hardy

University of North Carolina at Charlotte, Department of Physics and Optical Science, 9201 University City Avenue, Charlotte, North Carolina 28223-0001, United States

Christopher R. Wilson

University of North Carolina at Charlotte, Department of Physics and Optical Science, 9201 University City Avenue, Charlotte, North Carolina 28223-0001, United States

Pierce B. Irby

McKay Department of Urology, Carolinas Medical Center, 1024 Edgehill Road South, Charlotte, North Carolina 28207, United States

Nathaniel M. Fried

University of North Carolina at Charlotte, Department of Physics and Optical Science, 9201 University City Avenue, Charlotte, North Carolina 28223-0001, United States

McKay Department of Urology, Carolinas Medical Center, 1024 Edgehill Road South, Charlotte, North Carolina 28207, United States

Johns Hopkins Medical Institutions, Department of Urology, 601 North Caroline Street, Baltimore, Maryland 21287, United States

J. Biomed. Opt. 19(12), 128001 (Dec 16, 2014). doi:10.1117/1.JBO.19.12.128001
History: Received September 12, 2014; Accepted November 12, 2014
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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=2120nm) was operated with standard parameters of 600 mJ, 350μs, 6 Hz, and 270-μm-core optical fiber. The TFL (λ=1908nm) was operated with 35 mJ, 500μs, 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 13.7ml/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±41s (n=12). TFL times measured 111±49, 39±11, and 23±4s, 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.

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© 2014 Society of Photo-Optical Instrumentation Engineers

Citation

Luke A. Hardy ; Christopher R. Wilson ; Pierce B. Irby and Nathaniel M. Fried
"Thulium fiber laser lithotripsy in an in vitro ureter model", J. Biomed. Opt. 19(12), 128001 (Dec 16, 2014). ; http://dx.doi.org/10.1117/1.JBO.19.12.128001


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