title: 70 vs 120 W thulium:yttrium-aluminium-garnet 2 microm continuous-wave laser for the treatment of benign prostatic hyperplasia: a systematic ex-vivo evaluation.
abstract: OBJECTIVE
  To evaluate the ablative and haemostatic properties of the recently introduced 120-W thulium:yttrium-aluminium-garnet (Tm-YAG) laser and to assess these results against those of the previously introduced 70-W Tm-YAG laser.
  
  
  METHODS
  The ex-vivo model of the isolated blood-perfused porcine kidney was used to determine the ablation capacity, haemostatic properties and coagulation depth of a 2 microm continuous-wave Tm-YAG laser. The energy was delivered using a 550-microm and an 800-microm bare-ended fibre. The results of the recently introduced 120-W Tm-YAG were compared to the established 70-W device. Kidney tissue was embedded for histological evaluation. After staining (haematoxylin and eosin, H & E; and NADH) of the specimen, the coagulation zone and depth of the necrotic tissue layer were measured.
  
  
  RESULTS
  With increased power output, the mean (sd) rate of vaporization of tissue increased, from 9.80 (3.03) g/10 min at 70 W to 16.41 (5.2) g/10 min at 120 W using the 550 microm fibre. The total amount of ablated tissue using the 800 microm fibre was lower than with the 550 microm fibre. With increasing power output the bleeding rate remained stable in either group. Tissue penetration remained shallow, even with increasing power output. In contrast to H&E staining, where the coagulation zone was measured, NADH staining showed an inner zone of necrotic tissue, again with no difference between the 70- and the 120-W Tm-YAG.
  
  
  CONCLUSIONS
  The 120-W Tm-YAG offers significantly higher ablation rates than the 70-W device, and despite the increased rate of ablation with the 120-W Tm-YAG, the bleeding rate and depth of tissue penetration were comparable to those using the 70-W device.
authors.affiliation: Department of Urology, University Medical Centre Mannheim, Mannheim, Germany. thorsten.bach@umm.de
authors.forename: Thorsten
authors.initials: T
authors.lastname: Bach
authors.forename: Nina
authors.initials: N
authors.lastname: Huck
authors.forename: Felix
authors.initials: F
authors.lastname: Wezel
authors.forename: Axel
authors.initials: A
authors.lastname: Häcker
authors.forename: Andreas J
authors.initials: AJ
authors.lastname: Gross
authors.forename: Maurice Stephan
authors.initials: MS
authors.lastname: Michel
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D007668:Kidney / Q000601:surgery*; D053685:Laser Therapy / Q000379:methods* / Q000592:standards; D053844:Lasers, Solid-State / Q000592:standards / Q000627:therapeutic use*; D008297:Male; D011470:Prostatic Hyperplasia / Q000601:surgery*; D013552:Swine; D013932:Thulium / Q000627:therapeutic use*
chemical_list: D013932:Thulium