title: Optimal power settings for Holmium:YAG lithotripsy.
abstract: OBJECTIVE
  We determined the optimal Ho:YAG lithotripsy power settings to achieve maximal fragmentation, minimal fragment size and minimal retropulsion.
  
  
  METHODS
  Stone phantoms were irradiated in water with a Ho:YAG laser using a 365 μm optical fiber. Six distinct power settings were tested, including 0.2 to 2.0 J and 10 to 40 Hz. For all cohorts 500 J total radiant energy were delivered. A seventh cohort (0.2 J 40 Hz) was tested post hoc to a total energy of 1,250 J. Two experimental conditions were tested, including with and without phantom stabilization. Total fragmentation, fragment size and retropulsion were characterized. In mechanism experiments using human calculi we measured crater volume by optical coherence tomography and pressure transients by needle hydrophone across similar power settings.
  
  
  RESULTS
  Without stabilization increased pulse energy settings produced increased total fragmentation and increased retropulsion (each p <0.0001). Fragment size was smallest for the 0.2 J cohorts (p <0.02). With stabilization increased pulse energy settings produced increased total fragmentation and increased retropulsion but also increased fragment size (each p <0.0001). Craters remained symmetrical and volume increased as pulse energy increased. Pressure transients remained modest at less than 30 bars even at 2.0 J pulse energy.
  
  
  CONCLUSIONS
  Holmium:YAG lithotripsy varies as pulse energy settings vary. At low pulse energy (0.2 J) less fragmentation and retropulsion occur and small fragments are produced. At high pulse energy (2.0 J) more fragmentation and retropulsion occur with larger fragments. Anti-retropulsion devices produce more efficient lithotripsy, particularly at high pulse energy. Optimal lithotripsy laser dosimetry depends on the desired outcome.
authors.affiliation: Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Jason
authors.initials: J
authors.lastname: Sea
authors.forename: Lee M
authors.initials: LM
authors.lastname: Jonat
authors.forename: Ben H
authors.initials: BH
authors.lastname: Chew
authors.forename: Jinze
authors.initials: J
authors.lastname: Qiu
authors.forename: Bingqing
authors.initials: B
authors.lastname: Wang
authors.forename: John
authors.initials: J
authors.lastname: Hoopman
authors.forename: Thomas
authors.initials: T
authors.lastname: Milner
authors.forename: Joel M H
authors.initials: JM
authors.lastname: Teichman
mesh_terms: D000704:Analysis of Variance; D006695:Holmium; D006801:Humans; D066298:In Vitro Techniques; D053844:Lasers, Solid-State; D017602:Lithotripsy, Laser / Q000295:instrumentation / Q000379:methods*; D014545:Urinary Calculi / Q000628:therapy*
chemical_list: D006695:Holmium