70 vs 120 W thulium:yttrium-aluminium-garnet 2 μm continuous-wave laser for the treatment of benign prostatic hyperplasia: a systematic ex-vivo evaluation

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. MATERIALS AND 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 mu m continuous-wave Tm-YAG laser. The energy was delivered using a 550-mu m and an 800-mu m 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 mu m fibre. The total amount of ablated tissue using the 800 mu m fibre was lower than with the 550 mu m 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. CONCLUSION 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.