BPH/LUTS: Electrosurgery, Lasers & Other Technology

Moderated Poster Session

MP3-17 - Effect of Distance between Tissue and Laser Fiber on the Size of the Coagulation Zone: an In-vitro Study of Laser-Tissue Interaction.

Presenting Author(s)

• 

  Mark Taratkin, MD

  Researcher
  Institute for Urology, Sechenov University

Author(s)

• 

  Dmitry Enikeev, MD, PhD

  Deputy Director for Science
  Institute for Urology and Reproductive health, Sechenov University
• PG

  Petr Glybochko

  Director
  RI for Uronephrology, Sechenov University
• LR

  Leonid Rapoport

  Deputy Director
  RI for Uronephrology, Sechenov University
• 

  Christopher Netsch, MD, Ass Prof

  Consultant
  Asklepios Klinik Barmbek, Abteilung für Urologie
• 

  Benedikt Becker

  Resident
  Asklepios Klinik Barmbek, Department of Urology
• AG

  Andreas J. Gross

  Head of Department
  Asklepios Klinik Barmbek, Abteilung für Urologie

Introduction & Objective :

Laser-tissue interaction is based on the physical properties (i.e. wavelength) of the laser and variables such as laser power, pulse length and distances of the laser fiber tip to the tissue surface. The objective of this study was to estimate how the distance between tissue and the laser fiber tip alters laser-tissue interaction in different types of lasers.

Methods :

Tissue samples from fresh non-frozen porcine kidney were used to compare 4 lasers with an average power of 60-W using a 600 µm bare-ended fiber: a continuous wave Thulium fiber laser (cwTFL), a Super Pulse (SP) TFL, a Ho:YAG laser, and a Blue Diode Laser (BDL) (wavelength of 0.45 µm, comparable with Greenlight laser). We used a XY translation stage with a fixed fiber holder which allowed changing the gap between tissue and fiber with precision ± 0.1 mm by micrometer screw. The water filled gap between fiber and tissue was varied in a range from 0 mm to 6 mm. Exposure time was fixed at 1 sec for each laser. Afterwards, the tissue samples were sliced with a microtome for subsequent Lactat Dehydrogenase (LDH) staining to determine zones of thermal damage, vaporization, and coagulation.

Results : Characteristics of the lasers, laser settings, and the results of histology evaluation are shown in Table 1. In contact mode (0 mm gap), CWTFL produces the largest coagulation zone. This may be due to better absorption of CWTFL energy by intracellular water, which leads to deepest incision. On the other hand, coefficient of absorption in water for the Ho:YAG laser is lower than CWTFL, resulting in larger coagulation and smaller ablation zones. At 2 mm, only the Ho:YAG laser vaporized tissue. Which is linked to thermo-mechanical impact caused by a stream of bubbles of vaporizing water. Coagulation effect of BDL remained up to maximum gap of 6 mm.

Conclusions :

CWTFL must be at a distance of 2mm from the tissue to produce superficial coagulation; the Ho:YAG laser produced thermomechanical damage to tissue at the largest distance; the BDL has the strongest coagulation effect among the three lasers, with no significant changes in its depth of coagulation at different distances.