title: Laser fibre deterioration and loss of power output during photo-selective 80-w potassium-titanyl-phosphate laser vaporisation of the prostate.
abstract: BACKGROUND
  The potassium-titanyl-phosphate (KTP) laser technique for photo-selective vaporisation of the prostate (PVP) has been regularly improved over the last decade. Nonetheless, decreasing efficiency of tissue vaporisation during the course of the operation and macroscopic alterations of the laser fibre's tip are regularly observed and seem to affect the outcome of this procedure.
  
  
  OBJECTIVE
  To investigate the course of power output and to determine the type and extent of fibre deterioration during PVP.
  
  
  METHODS
  Forty laser fibres were investigated during PVP in 35 consecutive patients with prostatic bladder outflow obstruction between January 2007 and August 2007 in a university hospital.
  
  
  METHODS
  All patients underwent PVP performed by three different surgeons using the 80-W KTP laser.
  
  
  METHODS
  Power output was measured at the beginning and regularly throughout PVP and throughout in vitro vaporisation without fibre-tissue contact. Microscopic documentation of the fibre tip was performed after the procedure.
  
  
  CONCLUSIONS
  Carbonisation and melting of the fibre tip was regularly visible and appeared to be more pronounced as more energy was applied. Additionally, 90% of the fibres showed a significant decrease of power output during PVP, resulting in an end-of-lifespan (ie, 275-kilojoule) median power output of 20% of the initial value. Final median power output after in vitro vaporisation was 83% of the starting value. The extent of the structural and functional changes might only be valid for the operative technique performed in this investigation.
  
  
  CONCLUSIONS
  Fibre deterioration caused significant reduction of power output during PVP. This finding is an explanation for the often observed decreasing efficiency of tissue ablation and may also be responsible for some of the typical drawbacks and complications of PVP. Hence, improvements in fibre quality are necessary to advance the efficiency of this technique.
authors.affiliation: Department of Urology, University of Zürich, University Hospital, Zürich, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hermanns
authors.forename: Tullio
authors.initials: T
authors.lastname: Sulser
authors.forename: Markus
authors.initials: M
authors.lastname: Fatzer
authors.forename: Martin K
authors.initials: MK
authors.lastname: Baumgartner
authors.forename: Julien M
authors.initials: JM
authors.lastname: Rey
authors.forename: Markus W
authors.initials: MW
authors.lastname: Sigrist
authors.forename: Hans-Helge
authors.initials: HH
authors.lastname: Seifert
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D004560:Electricity; D004868:Equipment Failure; D006801:Humans; D053844:Lasers, Solid-State; D008297:Male; D008875:Middle Aged; D020728:Transurethral Resection of Prostate / Q000295:instrumentation*