Presented by: Luigi Candela MD
Division of Experimental Oncology, Unit of Urology, URI, IRCCS Ospedale San Raffaele, Milan, Italy. Università Vita-Salute San Raffaele.

Introduction

Endourological laser applications in the upper urinary tract result in heat generation. Several laboratory experiments have been carried out to characterize fluid temperature during laser activation. However, an analysis of spatial distribution of generated heat has never been performed before. We aimed at assessing heat generation and distribution in an in-vitro caliceal model during both Ho:YAG and thulium fiber laser (TFL) activation.

Materials

The experimental setup consisted of a glass pipette with an open roof bulb n a 37°C water bath simulating a renal calyx (Figure 1a). Two different scenarios were analyzed:

1) laser activation without irrigation.

2) laser activation with irrigation (saline), with an irrigating pressure set at 40 mmHg and the laser fiber conducted through a flexible ureteroscope working channel (Lithovue, Boston Scientific) inserted through a 12-14 ureteral access sheath

In both cases, the laser fiber was activated at the center of the calyx. For live temperature monitoring during laser activation, a thermal camera was placed perpendicular to the open roof of the pipette bulb. All test were performed using an high power Ho:YAG laser generator set with the lowest available peak power (Cyber Ho 150 W, Quanta System) and a Thulium Fiber Laser set with the highest available peak power (TFL, FiberDust 60W, Quanta System). The spatial and temporal temperature fluctuations were documented with a thermal camera (T865, resolution 640x480 px, FLIR) and recorded during 60 seconds of uninterrupted laser activation, at different power and frequency settings with or without irrigation. Tested powers were 5 W, 10 W, 20 W, and 40 W. Each experimental configuration was repeated at least three times to ensure reliable results. Descriptive statistics was used to compare Ho:YAG and TFL peak temperature, as well as time required to reach 43°C temperature at 2 mm distance from the laser fiber tip.

Results

,

Figure 1b and 1c graphically report the relationship between laser activation time and special distribution of generated heat for Ho:YAG and TFL respectively, showing a similar profile. No difference was found between the two lasers regarding both peak temperatures and time to reach 43°C at 2 mm distance from the laser fiber tip (all p>0.05), irrespectively of irrigation.

Conclusion

TFL and Ho:YAG laser show similar profile both in temperature rise and spatial distribution of generated heat.

Funding

none

Co-Authors

Daniele Robesti, MD
Division of Experimental Oncology, Unit of Urology, URI, IRCCS Ospedale San Raffaele, Milan, Italy. Università Vita-Salute San Raffaele.

Margherita Fantin, MD
Division of Experimental Oncology, Unit of Urology, URI, IRCCS Ospedale San Raffaele, Milan, Italy. Università Vita-Salute San Raffaele.

Christian Corsini, MD
Division of Experimental Oncology, Unit of Urology, URI, IRCCS Ospedale San Raffaele, Milan, Italy. Università Vita-Salute San Raffaele.

Luca Villa, MD
Division of Experimental Oncology, Unit of Urology, URI, IRCCS Ospedale San Raffaele, Milan, Italy. Università Vita-Salute San Raffaele.

Ioannis Kartalas Goumas, MD
Department of Urology, Istituto Clinico Beato Matteo, 27029 Vigevano, Italy.

Silvia Proietti, MD
Department of Urology, IRCCS San Raffaele Hospital, Milan, Italy. European Training Center in Endourology, Milan, Italy

Guido Giusti, MD
Department of Urology, IRCCS San Raffaele Hospital, Milan, Italy. European Training Center in Endourology, Milan, Italy

Cesare Scoffone, MD
Department of Urology, Cottolengo Hospital, Torino, Italy.

Cecilia Cracco, MD
Department of Urology, Cottolengo Hospital, Torino, Italy.

Olivier Traxer, MD
Urology Unit, Tenon Hospital, Paris, France

Francesco Montorsi, MD
Division of Experimental Oncology, Unit of Urology, URI, IRCCS Ospedale San Raffaele, Milan, Italy. Università Vita-Salute San Raffaele.

Esteban Emiliani,
Department of Urology, Fundación puigvert. Universidad Autónoma de Barcelona

Etienne Keller, MD
Department of Urology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.

Andrea Salonia, MD
Division of Experimental Oncology, Unit of Urology, URI, IRCCS Ospedale San Raffaele, Milan, Italy. Università Vita-Salute San Raffaele.

Paola Saccomandi,
Department of Mechanical Engineering, Politecnico di Milano, Milan, Italy

Eugenio Ventimiglia,
Division of Experimental Oncology, Unit of Urology, URI, IRCCS Ospedale San Raffaele, Milan, Italy. Università Vita-Salute San Raffaele.