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

Introduction

Among laser sources, the pulse profiles differ. Two lasers stand out: Holmium:YAG(Ho:YAG) with a non-uniform profile and Thulium Fiber Laser(TFL) with a regular and uniform profile, with an immediately maximum amplitude stable over time. Recently, pulsed-Thulium:YAG (p-Tm:YAG) has been proposed as an alternative. The objective of our study was to compare p-Tm:YAG and TFL pulse profiles.

Materials

Two laser generators were used (100Wp-Tm:YAG (Thulio®, Dornier, Germany) and 60W-TFL (EMS, Switzerland)) with 270µm laser fibers. Average power and pulse profiles were acquired using a wattmeter and an oscilloscope (InfiniiVision DSO5014A (Agilent Technologies®)), the fiber is put in an integrating sphere with a photodiode sensor. We used different settings between 3 and 10W. Settings are displayed in Table 1 and the set-up is presented in Figure 1.  Fibers were cut with ceramic scissors and stripped between each test, repeated three times. The peak power (PP) was calculated for each parameter (average power(W)/(frequency(Hz)xPulse duration(s)).

Results

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Tm:YAG presented a uniform and stable over the time profile, regardless to pulse modulation : dusting, fragmenting, captive fragmenting, soft tissue, flex short pulse and flex long pulse. The PP ranged from 561W to 2228Wwith a difference of PP and pulse duration following pulse mode set on generator.

For the TFL, we set the laser on 500W corresponding to PP3.  For all settings, we obtained a PP which still constant around 430 and 503W (mean value : 449W) with always a uniform profile. The p-Tm:YAG PP was always higher than the TFL one which remained fixed. Only the pulse duration increased with energy.

Conclusion

The p-Tm:YAG presents a stable uniform profile superimposable to that of the TFL contrary to the Ho:YAG laser. The peak power, varying from 500 to 2200W, is intermediate between Ho:YAG and TFL lasers. Several pulse modulations are available but preclinical and clinical data are lacking to define the place of each during lithotripsy.

Funding

none

Lead Authors

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

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

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

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

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