Pulsed Lasers and Endocorporeal Laser Lithotripsy – Beyond the Abstract

Endocorporeal Laser Lithotripsy (ELL) was firstly described in 1992, having the Holmium: Yttrium-Aluminium-Garnet(Ho: YAG) pulsed laser as a pioneer in the field and then, turning into the current gold standard laser for this procedure. Thanks to the technological advances, nowadays we have a new pulsed laser gaining access in ELL, the Thulium Fiber Laser (Tm-Fiber). Tm-Fiber laser has arrived to, perhaps, become the new gold standard.



Pulsed lasers are the only ones that can play a role in EEL, producing bursts of light spaced in time, which means that between each emission, there is no light production. The fundamentals of this type of pulsed mode are period, pulse rate, pulse duration, pulse energy, power, and laser pulse modulation. In general terms, period is the time between the initiation of one laser pulse and the start of the next one; pulse rate, the number of laser pulses during a single second; pulse duration can be short or long; pulse energy (J) represents the intensity of a laser pulse during a period; power can be subdivided in peak power, instantaneous power or average power; and laser pulse modulation, where Moses effect has regained popularity due to the development of double laser pulses. The aim of this update was to define in a more precise way the fundamentals of pulsed lasers for better understanding and to compare both laser technologies available in the market.

In terms of technology, they differ in the amplifying medium, which is crystal YAG for Ho: YAG laser and thulium ions-doped fiber for Tm-fiber laser; and also, in the pumping system that is a flash lamp for the Ho: YAG laser and a laser diode for the Tm-fiber. The latter having also the lowest laser fiber core diameter (50µm). On the other side, in terms of laser settings, it is important to remark that Ho: YAG laser reaches a higher power when faced to the Tm-fiber (120W vs 60W respectively) but the pulse rate range is much higher with Tm-fiber (until 2000 Hz). One of the novelties of this new laser is the double pulse and peak power, not seen before.

In summary, our update shows that even if setting the pulse energy and rate is important for optimize the stone treatment, the future of ELL rests on the pulse modulation, which remains not that well-known in the current practice. After comparing both, Ho:YAG and Tm-Fiber lasers, it seems that Tm-Fiber overcomes the Ho: YAG technological limits.

Written by: Frédéric Panthier MD MSc, Mariela Corrales MD, Steeve Doizi MD MSc and Olivier Traxer PhD

GRC n(o)20, groupe de recherche clinique sur la lithiase urinaire, hôpital Tenon, Sorbonne université, 75020 Paris, France; Service d'urologie, Assistance publique-Hôpitaux de Paris, hôpital Tenon, Sorbonne université, 4, rue de la Chine, 75020 Paris, France; Service d'urologie, Assistance publique-Hôpitaux de Paris, hôpital européen Georges-Pompidou, université de Paris, 20, rue Leblanc, 75015 Paris, France. Electronic address: ., GRC n(o)20, groupe de recherche clinique sur la lithiase urinaire, hôpital Tenon, Sorbonne université, 75020 Paris, France; Service d'urologie, Assistance publique-Hôpitaux de Paris, hôpital Tenon, Sorbonne université, 4, rue de la Chine, 75020 Paris, France. Electronic address: ., GRC n(o)20, groupe de recherche clinique sur la lithiase urinaire, hôpital Tenon, Sorbonne université, 75020 Paris, France; Service d'urologie, Assistance publique-Hôpitaux de Paris, hôpital Tenon, Sorbonne université, 4, rue de la Chine, 75020 Paris, France. Electronic address: ., GRC n(o)20, groupe de recherche clinique sur la lithiase urinaire, hôpital Tenon, Sorbonne université, 75020 Paris, France; Service d'urologie, Assistance publique-Hôpitaux de Paris, hôpital Tenon, Sorbonne université, 4, rue de la Chine, 75020 Paris, France. Electronic address: .

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