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

Abstract

μ 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. RESULTSWith 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 μ m fibre. The total amount of ablated tissue using the 800 μ m fibre was lower than with the 550 μ 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. CONCLUSIONThe 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. KEYWORDSbenign prostatic enlargement, tissue ablation, coagulation, thulium : YAG, laser Study Type -Aetiology (case series) Level of Evidence 4 OBJECTIVETo 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 METHODSThe ex-vivo model of the isolated bloodperfused porcine kidney was used to determine the ablation capacity, haemostatic properties and coagulation depth of a 2 μ m continuous-wave Tm-YAG laser. The energy was delivered using a 550-μ m and an 800-

In vitro comparison of the vaporesection of human benign prostatic hyperplasia using 70- and 120-W 2-µm lasers

“…To further evaluate this effect, NADH staining was used to evaluate the histological effects of the 2-mm lasers; NADH staining is currently the best means of determining cellular viability and has the potential to clearly identify energy effects in these two layers. In the current study, the penetration depth (necrotic layer) remained unchanged with increasing laser power output (0.9860.13 and 0.9960.12 mm at 70 and 120 W, respectively), and these results are consistent with those reported by Bach et al 8 in porcine kidneys (1.0960.14 and 1.0960.24 mm at 70 and 120 W, respectively). Both the coagulation zone and necrotic tissue were superficial because most of the heat that originated during vaporesection was lost by a continuous saline flush during the operation; the effect of heat penetration is therefore very weak.…”

“…14 Therefore, knowledge about the depth of damaged tissue is essential to estimate the risk of unintended collateral tissue damage. Our results showed that the extent of the coagulation zone was similar between the 70-and 120-W groups (0.3060.09 and 0.3160.08 mm, respectively), which is consistent with the report by Bach et al 8 using porcine kidney tissue (0.3660.02 mm for 70-W laser and 0.4060.04 mm using a 120-W laser). Furthermore, the tissue below this coagulation zone inevitably experiences some heat penetration, which might cause cellular damage.…”

“…A major question of this study was whether the speed of vaporesection of human prostate tissue could be improved by increasing the laser power from 70 to 120 W. Bach et al 8 reported that the mean speed of resection of porcine kidneys was 9.8063.03 g/10 min for 70 W and 16.4165.20 g/10 min for 120 W, demonstrating that the 120-W Tm:YAG laser (RevoLix; Lisa Laser Products) offered significantly higher ablation rates than the 70-W device. In our current study, the speed of vaporesection of prostatic tissue was 5.2160.66 g/5 min for the 70-W group and 10.3961.15 g/5 min for the 120-W group, indicating that the 120-W 2-mm laser exhibited higher vaporesected rates than the 70-W laser; the mean speed of vaporesection with the 120-W laser increased twofold over that with the 70-W laser.…”

“…With the upgrade of 2-mm laser device from 70 to 120 W, the investigator was interested in the difference between two kinds of output laser. 8 However, due to different power outputs, the clinical effects are likely different. However, the comparison of the two laser outputs with regard to their clinical efficacy, vaporesection speed and penetration depth remains unclear.…”

Thulium:YAG VapoEnucleation of the prostate in large glands: a prospective comparison using 70- and 120-W 2-µm lasers

“…14 Bach et al 15 recently analysed the ablation capacities of the 70-and 120-w Tm:YAG devices in an ex vivo model. They found higher tissue vaporisation rates with the 120-w Tm:YAG device than with the 70-w device, despite comparable bleeding rates and tissue penetration.…”