Presented by: Marie Chicaud MD
Service d'urologie, CHU de Limoges

Introduction

Holmium:YAG(Ho:YAG) and  Thulium Fiber Laser(TFL) are commonly used for laser lithotripsy. Recently, a new pulsed-Thulium:YAG(p-Tm:YAG) has been proposed as an alternative. The Fiber Output Power(FOP) is a main determinant of laser lithotripsy, and differs from power set on generator(PSG). We aimed to determinate the power loss(PL) between FOP and PSG among laser sources and settings. 

Materials

In this in vitro study, we used four laser generators (Ho:YAG (120W-Cyber-Ho,Quanta®,USA), two TFL(Coloplast®, USA and EMS®, Switzerland) and p-Tm:YAG(100W-Thulio,Dornier®,Munich)), and similar laser fiber diameter(200-272mm). First, we measured with a wattmeter(Molectron EPM1000, Coherent Inc®, USA) the average powers before and after 30 and 60 seconds of continuous activation in saline solution then in contact with a stone phantoms(BegoStone,Bego©). Between each measures the fiber was cut with ceramic scissors and stripped. Different settings were used to have a power of 10 or 15W(table 1). Set-up is presented in Figure 1. PL were quantified as percentage between FOP and PSG, and compared among laser sources and generators. 

Results

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In saline at 10W, the PP was 27.35% for Ho:YAG, 9.2% for EMS-TFL, 15.19% for COLOPLAST-TFL and 16.53% for p-Tm:YAG. At 15W, the PP was 28% for Ho:YAG, 13.27% for EMS-TFL, 15.47% for COLOPLAST-TFL and 13.67% for p-Tm:YAG. After 30s of laser activation, the FOP was better than at the beginning by about 1% and without variation at 60s. For all lasers and settings, FOP and PSG were significantly different(p < 0.05), however no difference in PP between PSF-T0 and T30 and T60. We obtained similar results against synthetic calculations. Comparing laser sources at the same setting(1J,10Hz), the PL of Ho:YAG was significantly different from other laser sources(p<0.05).

Conclusion

Urologists should consider FOP during laser lithotripsy, which differs consistently from the PSG. After an initial loss the output power seems to stay sand. The PL of the Ho:YAG seems almost twice more than the TFL and the pTm:YAG, which are not different. This should be considered in clinical practice and in fiber preservation.

Funding

None

Lead Authors

Stessy Kutchukian, MD
Service d'urologie, CHU de Poitiers

Laurent Berthe, PHD
PIMM, UMR 8006 CNRS-Arts et Métiers ParisTech

Catalina Solano, MD
Service d'urologie, APHP, Hôpital Tenon

Luigi Candela, MD
Division of experimental oncology/unit of Urology, URI, IRCCS Ospedale San Raffaele, Milan, Italy; Vital-Salute San Raffaele University,

Steeve Doizi, Md PHD
Service d'urologie, APHP, Hôpital Tenon

Olivier Traxer, MD
Service d'urologie, APHP, Hôpital Tenon

Frederic Panthier, MD, MSc
Service d'urologie, APHP, Hôpital Tenon