title: Variable Pulse Duration From a New Holmium:YAG Laser: The Effect on Stone Comminution, Fiber Tip Degradation, and Retropulsion in a Dusting Model.
abstract: OBJECTIVE
  To more clearly define the efficiency and potential benefits of variable pulse-width laser technology for ureteroscopic lithotripsy, we performed comparative in vitro evaluations assessing stone comminution, laser fiber tip degradation, and stone retropulsion.
  
  
  METHODS
  All experiments were conducted using a Swiss LaserClast Holmium:YAG laser (Electro Medical Systems, Nyon, Switzerland) with adjustable pulse duration (300 µs-1500 µs). To assess comminution efficiency and fiber tip degradation, a "dusting" model was employed; the laser fiber tip was moved by a 3-dimensional positioning system in a spiral motion across a flat BegoStone surface submerged in water. Comminution efficiency was measured as the loss of stone mass while fiber tip degradation was measured simultaneously. The same laser and fiber were used in a pendulum model to measure stone retropulsion with a high-speed resolution camera.
  
  
  RESULTS
  In our dusting model, comminution was significantly greater at high energy (2 J/5 Hz). At the high energy setting, comminution was significantly greater with long pulse duration than short pulse, although this difference was not seen at the high frequency setting (1 J/10 Hz). Tip degradation was increased at high energy settings and was even more pronounced with short pulse duration than long pulse. Short pulse duration caused far more retropulsion than the long pulse setting.
  
  
  CONCLUSIONS
  In an in vitro dusting model, a longer laser pulse duration provides effective stone comminution with the advantage of reducing laser fiber tip degradation and stone retropulsion.
authors.affiliation: Division of Urologic Surgery, Duke University Medical Center, Durham, NC. Electronic address: Daniel.wollin@duke.edu.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Wollin
authors.affiliation: Division of Urologic Surgery, Duke University Medical Center, Durham, NC.
authors.forename: Anika
authors.initials: A
authors.lastname: Ackerman
authors.affiliation: Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC.
authors.forename: Chen
authors.initials: C
authors.lastname: Yang
authors.affiliation: Division of Urologic Surgery, Duke University Medical Center, Durham, NC.
authors.forename: Tony
authors.initials: T
authors.lastname: Chen
authors.affiliation: Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC.
authors.forename: Walter Neal
authors.initials: WN
authors.lastname: Simmons
authors.affiliation: Division of Urologic Surgery, Duke University Medical Center, Durham, NC.
authors.forename: Glenn M
authors.initials: GM
authors.lastname: Preminger
authors.affiliation: Division of Urologic Surgery, Duke University Medical Center, Durham, NC.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Lipkin
mesh_terms: D004867:Equipment Design; D006339:Heart Rate; D006695:Holmium; D006801:Humans; D053844:Lasers, Solid-State / Q000627:therapeutic use*; D017602:Lithotripsy, Laser; D019047:Phantoms, Imaging; D016896:Treatment Outcome; D014514:Ureteral Calculi / Q000628:therapy*
chemical_list: D006695:Holmium