Category: BPH/LUTS: Electrosurgery, Lasers & Other Technology

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.

Thu, Sep 20
4:00 PM - 6:00 PM

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.

Mark Taratkin

Institute for Urology, Sechenov University
Moscow, Moskva, Russia

Researcher at the Institute for Urology and Reproductive health, Sechenov University.
Head of the laser technology lab.

Dmitry Enikeev

Deputy Director for Science
Institute for Urology and Reproductive health, Sechenov University
Moscow, Moskva, Russia

Surgical experience:
Experienced in TURP (>300 surgeries).
Experienced in upper urinary tract endosurgery (PCNL >200, RIRS >200).

2008-Present: Multiple upper and lower urinary tract surgeries;
2011-Present: HoLEP (400 surgeries);
2011-Present: En-bloc enucleation of bladder tumor (50 surgeries);
2016-Present: ThuLEP (>400 surgeries);
2016-Present: Thulium en-bloc enucleation of bladder tumor (>80 surgeries);
2016-Present: Brachytherapy (>40 surgeries); prostate cryoablation (70 surgeries), renal cancer cryoablation (30 surgeries);
Apr 2017-Present: Irreversible electroporation (10 surgeries);
Apr 2017-Present: MR-fusion prostate biopsy (80 procedures).

Petr Glybochko

RI for Uronephrology, Sechenov University
Moscow, Moskva, Russia

Leonid Rapoport

Deputy Director
RI for Uronephrology, Sechenov University
Moscow, Moskva, Russia

Christopher Netsch

Asklepios Klinik Barmbek, Abteilung für Urologie
Hamburg, Hamburg, Germany

Dr. med. Dr. habil. Christopher Netsch, MD, FEBU is an Assistant Professor of Urology at the Semmelweis University of Budapest/Hungary. He received his medical degree from the University of Mainz/Germany. His training in urology was conducted at the Inselspital Bern/Switzerland, Städtisches Klinikum Karlsruhe/Germany and at the Asklepios Klinik Barmbek/Germany. After his board certification in 2011 (Hamburg/Germany), Dr. Netsch became a consultant urologist at the Asklepios Klinik Barmbek/Germany. Dr. Netsch completed his Endourology Fellowship at the Asklepios Klinik Barmbek in 2012. He was also qualified as a Fellow of the European Board of Urology (FEBU) in 2015.
Dr. Netsch`s research focuses on urolithiasis and minimally-invasive therapies for BPH. He has authored or co-authored over 70 peer-reviewed journal articles and numerous book chapters. He was awarded with the Mauermayer award of the German Society of Urology (DGU) in 2013 and the Hans Marberger award of the European Association of Urology (EAU) in 2014. He is currently an editorial consultant for the World Journal of Urology.
Dr. Netsch is a member of the DGU Urolithiasis Guidelines committee. He is also an active member of numerous national and international societies such as the DGU, EAU, and the Endourological Society. He is also a member of the DGU working group in Endourology and the EAU section of Uro-Technology (ESUT): Lower Tract Section.

Benedikt Becker

Asklepios Klinik Barmbek, Department of Urology
Hamburg, Hamburg, Germany

Dr. Becker is a resident of urology in the urological department of the Asklepios Hospital Barmbek in Hamburg, Germany. He studied in Giessen and Lübeck (both Germany). His main scientific interest is the broad spectrum of endourology, especially laser treatment of benign prostatic obstruction. He is an active member of the German Society of Urology (DGU), the German Society of Residents in Urology (GeSRU), and the Endourological Society (WCE). At this time, he is participating in the Two Year fellowship program in Endourology/Stone Surgery.

Andreas J. Gross

Head of Department
Asklepios Klinik Barmbek, Abteilung für Urologie
Hamburg, Hamburg, Germany