title: The effect of laser-fiber sweeping speed on the efficiency of photoselective vaporization of the prostate in an ex vivo bovine model.
abstract: BACKGROUND
  Recommendations for efficient photoselective vaporization of the prostate (PVP) include a side-to-side rotational laser-fiber "sweeping" motion, yet scientific study of this technique is lacking. We investigated whether the speed of laser-fiber sweeping affects tissue vaporization efficiency.
  
  
  METHODS
  PVP was performed using the 120-W GreenLight high-performance system. Video analysis of a surgeon performing PVP was carried out to identify sweeping speeds used clinically. PVP efficiency was subsequently tested at four different sweeping speeds using two manipulations of an ex vivo bovine prostate model, including (1) excised prostate tissues (n = 40) in a vaporization chamber equipped with motorized laser-fiber movements; (2) retrograde endoscopic vaporization (n = 80) within whole lower urinary tracts. Vaporized cavity sizes and coagulative margins were measured by liquid-paraffin molding and histologic cross-sectioning approaches.
  
  
  RESULTS
  Video analysis of clinical PVP showed wide variability in sweeping speed, mostly ranging between 0.5 and 2.0 (mean 1.50) sweeps/second. Using either manipulation of the ex vivo bovine prostate model described above, PVP at lower sweeping speeds (0.5 and 1.0 sweeps/second) removed significantly more tissue (up to twofold) compared with higher sweeping speeds (1.5 and 2.0 sweeps/second), with significant albeit minimal reductions in coagulation margins.
  
  
  CONCLUSIONS
  In this ex vivo prostate model, our results suggest that vaporization efficiency is compromised with faster laser-fiber sweeping. This finding counters principles of traditional transurethral resection of the prostate, in which faster axial movement toward the surgeon removes tissue more efficiently. This study highlights that PVP technique can be tested in a scientific manner, identifying optimal parameters for achieving maximal tissue vaporization efficiency.
authors.affiliation: Department of Urology, Weill-Cornell Medical Center, New York, New York, USA. erk9005@nyp.org
authors.forename: Eric C
authors.initials: EC
authors.lastname: Kauffman
authors.forename: Hyun Wook
authors.initials: HW
authors.lastname: Kang
authors.forename: Benjamin B
authors.initials: BB
authors.lastname: Choi
mesh_terms: D000818:Animals; D002417:Cattle; D004724:Endoscopy; D053685:Laser Therapy / Q000295:instrumentation* / Q000379:methods*; D008297:Male; D023421:Models, Animal; D011467:Prostate / Q000601:surgery*; D015203:Reproducibility of Results; D014741:Video Recording