title: Thulium fiber laser lithotripsy using tapered fibers.
abstract: BACKGROUND
  The Thulium fiber laser has recently been tested as a potential alternative to the Holmium:YAG laser for lithotripsy. This study explores use of a short taper for expanding the Thulium fiber laser beam at the distal tip of a small-core fiber.
  
  
  METHODS
  Thulium fiber laser radiation with a wavelength of 1,908 nm, 10 Hz pulse rate, 70 mJ pulse energy, and 1-millisecond pulse duration was delivered through a 2-m-length fiber with 150-microm-core-input-end, 300-microm-core-output-end, and 5-mm-length taper, in contact with human uric acid (UA) and calcium oxalate monohydrate (COM) stones, ex vivo (n = 10 each). Stone mass loss, stone crater depths, fiber transmission losses, fiber burn-back, irrigation rates, and deflection through a flexible ureteroscope were measured for the tapered fiber and compared with conventional fibers.
  
  
  RESULTS
  After delivery of 1,800 pulses through the tapered fiber, mass loss measured 12.7+/-2.6 mg for UA and 7.2+/-0.8 mg COM stones, comparable to conventional 100-microm-core fibers (12.6+/-2.5 mg for UA and 6.8+/-1.7 mg for COM stones). No transmission losses or burn-back occurred for the tapered fiber after 36,000 pulses, while a conventional 150-microm fiber experienced significant tip degradation after only 1,800 pulses. High irrigation rates were measured with the tapered fiber inserted through the working port of a flexible ureteroscope without hindering its deflection, mimicking that of a conventional 150 microm fiber.
  
  
  CONCLUSIONS
  The short tapered distal fiber tip allows expansion of the laser beam, resulting in decreased fiber tip damage compared to conventional small-core fibers, without compromising fiber bending, stone vaporization efficiency, or irrigation rates.
authors.affiliation: Department of Physics and Optical Science, University of North Carolina at Charlotte, Charlotte, North Carolina 28223-0001, USA.
authors.forename: Richard L
authors.initials: RL
authors.lastname: Blackmon
authors.forename: Pierce B
authors.initials: PB
authors.lastname: Irby
authors.forename: Nathaniel M
authors.initials: NM
authors.lastname: Fried
mesh_terms: D002129:Calcium Oxalate / Q000528:radiation effects*; D004867:Equipment Design; D006801:Humans; D017602:Lithotripsy, Laser / Q000295:instrumentation*; D055100:Optical Fibers; D013932:Thulium / Q000627:therapeutic use*; D046509:Tissue Culture Techniques; D020709:Ureteroscopes; D014527:Uric Acid / Q000528:radiation effects*; D014545:Urinary Calculi / Q000473:pathology / Q000601:surgery*
chemical_list: D002129:Calcium Oxalate; D014527:Uric Acid; D013932:Thulium