Poster session 5: Nephrolithiasis| Volume 8, ISSUE 8, P685, September 2009

C82 Urinary calculus and artificial sample fragmentation during Er:YAG and Ho:YAG lithotripsy in vitro

      Introduction and Objectives

      Laser-assisted lithotripsy is routinely used minimally invasive method in the clinical urological practices. The Holmium:YAG laser is the most recent addition. This laser based on the Yttrium-Aluminium-Garnet crystal with the source element Holmium emits beam of the wavelength of 2100 nm. More perspective and effective seems to be Erbium:YAG laser generating radiation of the wavelength of 2940 nm with higher water absorbtion.

      Material and Methods

      We compared the Ho:YAG and Er:YAG laser desintegration of the human calculi and the artificial plaster sample. In vitro we tested the routinely clinically used Coherent Versa Pulse Ho:YAG laser operating in free running regime, repetition rate of 5 Hz, radiation delivered by the 365 micron optical fibre and the laboratory flash-lamp pumped Ho:YAG and Er:YAG laser, repetition rate of 1 Hz, radiation delivered by the COP/Ag hollow waveguide sealed with fused silica cap. The stones of the known composition – whewellite, urinary acid dihydrate and the cubic plaster sample were irradiated at varying energy ranging from 25 mJ to 250 mJ in the Er:YAG laser and from 50 mJ to the clinical setting of 1500 mJ in the Ho:YAG laser. The perforation rate was measured according to the crater width, depth and number of pulses needed for the sample perforation at the variable energy.


      The optical microscope crater measuring in lower energy applications and the number of pulses counting in the sample perforation in higher energy applications showed the higher perforation rate of the Er:YAG laser radiation. We achieved almost twice higher efficiency in the human calculus and the artificial sample perforation and disruption.


      The Er:YAG laser is superior to the Ho:YAG laser for more efficient lithotripsy. In the relation with the documented more precise soft tissue cut and less surrounding tissue damage would be the ideal laser equipment for clinical urological use. The only limit is the cost of the flexible fibre.