<title>Erbium:YAG laser ablation of urethral and ureteral tissues</title>

Abstract

Cold knife incision of urological strictures results in a high rate of stricture recurrence. This study compares Ho:YAG and Er:YAG lasers for precise incision of urethral and ureteral tissues. Laser ablation was performed using Ho:YAG (?=2.1 µm) and Er:YAG (?=2.94 µm) lasers operating in long-pulse mode (?p = 300 µs). Ho:YAG laser radiation was delivered through low-OH fibers while Er:YAG laser radiation was delivered through germanium oxide or sapphire fibers. Ex vivo canine and porcine tissue samples were placed in saline, and perforation thresholds, ablation rates, and histological thermal damage measurements were recorded. Optical fiber damage thresholds during contact ablation were also studied. The Ho:YAG and Er:YAG lasers perforated thick tissue samples at thresholds of 350 J/cm2 and 65 J/cm2, respectively, with peripheral thermal damage zones measuring 290 + 30 µm and 30 + 10 µm, respectively. Germanium oxide fibers were damaged at energies greater than 150 mJ/pulse (80 JIcm2), but no damage to sapphire fibers was observed at energies up to 450 mJ/pulse (3 50 J/cm2). The Er:YAG laser efficiently ablates urethral and ureteral tissues while reducing peripheral thermal damage by an order of magnitude over the Ho:YAG laser. In vivo animal studies for Er:YAG laser incision of strictures are planned with comparison to cold knife incision.