title: Impact of pulse duration on Ho:YAG laser lithotripsy: treatment aspects on the single-pulse level.
abstract: OBJECTIVE
  Holmium-YAG (Ho:YAG) laser lithotripsy is a multi-pulse treatment modality with stochastic effects on the fragmentation. In vitro investigation on the single-pulse-induced effects on fiber, repulsion as well as fragmentation was performed to identify potential impacts of different Ho:YAG laser pulse durations.
  
  
  METHODS
  A Ho:YAG laser system (Swiss LaserClast, EMS S.A., Nyon, Switzerland) with selectable long- or short-pulse mode was tested with regard to fiber burn back, the repulsion capacity using an underwater pendulum setup and single-pulse-induced fragmentation capacity using artificial (BEGO) stones. The laser parameters were chosen in accordance with clinical application modes (laser fiber: 365 and 200 µm; output power: 4, 6 and 10 W in different combinations of energy per pulse and repetition rate). Evaluation parameters were reduction in fiber length, pendulum deviation and topology of the crater.
  
  
  RESULTS
  Using the long-pulse mode, the fiber burn back was nearly negligible, while in short-pulse mode, an increased burn back could be observed. The results of the pendulum test showed that the deviation induced by the momentum of short pulses was by factor 1.5-2 higher compared to longer pulses at identical energy per pulse settings. The ablation volumes induced by single pulses either in short-pulse or long-pulse mode did not differ significantly although different crater shapes appeared.
  
  
  CONCLUSIONS
  Reduced stone repulsion and reduced laser fiber burn back with longer laser pulses may result in a more convenient handling during clinical application and thus in an improved clinical outcome of laser lithotripsy.
authors.affiliation: Laser Research Laboratory (LFL) in LIFE-Centre, Hospital of University Munich, Feodor-Lynen-Str. 19, 81377, Munich, Germany, ronald.sroka@med.uni-muenchen.de.
authors.forename: Ronald
authors.initials: R
authors.lastname: Sroka
authors.forename: Thomas
authors.initials: T
authors.lastname: Pongratz
authors.forename: Gabriel
authors.initials: G
authors.lastname: Scheib
authors.forename: Wael
authors.initials: W
authors.lastname: Khoder
authors.forename: Christian G
authors.initials: CG
authors.lastname: Stief
authors.forename: Thomas
authors.initials: T
authors.lastname: Herrmann
authors.forename: Udo
authors.initials: U
authors.lastname: Nagele
authors.forename: Markus J
authors.initials: MJ
authors.lastname: Bader
mesh_terms: D006801:Humans; D053844:Lasers, Solid-State / Q000627:therapeutic use*; D017602:Lithotripsy, Laser / Q000379:methods*; D008953:Models, Anatomic; D013997:Time Factors; D016896:Treatment Outcome; D014545:Urinary Calculi / Q000628:therapy*