Ho: YAG and thulium fiber lasers exhibit comparable temperature distribution: an in vitro evaluation of thermal safety distances for endourological applications—section of EAU endourology
Robesti D. Corsini C. Perri D. Kwok J.-L. Tsaturyan A. Nedbal C. Villa L. Fossati N. Gallina A. Kartalas Goumas I. Salonia A. Gauhar V. Somani B.K. Traxer O. Saccomandi P. Ventimiglia E.
December 2025Springer Science and Business Media Deutschland GmbH
World Journal of Urology
2025#43Issue 1
Introduction: The concept of thermal safety distance upon laser activation has been recently introduced. We aimed to compare the thermal safety distance of Ho: YAG and thulium fiber laser (TFL) activation at different setups using an in vitro model. Methods: The experimental setup used a glass pipette with an open roof bulb in a 37 °C water bath to simulate a renal calyx. We analyzed two scenarios: (1) Laser activation without irrigation; (2) Laser activation at the center of the calyx with irrigation (saline at 40 cmH2O) via a flexible ureteroscope with a 12–14 Fr access sheath. Thermal camera tests were conducted using a Ho: YAG and TFL lasers. A thermal camera monitored the temperature for 60 s of laser activation at 5, 10, and 20 W, with and without irrigation. Each test was repeated three times. The Dewey and Sapareto formula was used to calculate cumulative equivalent minutes at 43 °C (CEM43), with a safety threshold of 120 min. The safety distance was defined as the minimum distance required to overcome the safety threshold. Results: We observed no differences both in recorded temperature values and in their temporal/spatial distribution (all p > 0.05). The safety threshold was not exceeded for either Ho: YAG or TFL lasers at 5 W, 10 W, and 20 W when irrigation was applied, with no statistically significant difference in safety distance between the two lasers (p > 0.05). Similarly, without irrigation, only the 20 W (Ho: YAG: 0.93 ± 0.11 mm, TFL: 0.84 ± 0.09 mm) settings exceeded the safety threshold, and no significant difference in safety distance was found between the lasers (p > 0.05). Conclusions: No differences in safety distance were observed between TFL and Ho: YAG lasers, regardless of irrigation or power settings. It is recommended for both lasers to remain below 20 W in absence of proper irrigation.
In vitro model , Laser temperature , Stone , Thermal dose , Thermal safety
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Vita-Salute San Raffaele University, Milan, Italy
Division of Experimental Oncology/Unit of Urology, URI, IRCCS Ospedale San Raffaele, Milan, Italy
Division of Urology, Sant’Anna Hospital, Via Ravona 20, San Fermo Della Battaglia, 22042, Italy
Department of Urology, Tan Tock Seng Hospital, Singapore, Singapore
Department of Urology and Andrology, Astana Medical University, Astana, Kazakhstan
Urology Unit, Azienda Ospedaliero-Universitaria Delle Marche, Università Politecnica Delle Marche, Ancona, Italy
Department of Surgery, Service of Urology, Ente Ospedaliero Cantonale (EOC), Lugano, Switzerland
Department of Urology, Istituto Clinico Beato Matteo, Vigevano, Italy
Department of Urology, Ng Teng Fong General Hospital, National University Health System, Singapore, Singapore
Department of Urology, University Hospital Southampton, Southampton, United Kingdom
Department of Urology, Tenon Hospital, Hôpitaux Universitaires Paris-Est, AP-HP, Université Pierre et Marie Curie Paris, Paris, France
Department of Mechanical Engineering, Politecnico di Milano, Milan, 20156, Italy
Department of Surgical Sciences, Uppsala University, Uppsala, Sweden
Vita-Salute San Raffaele University
Division of Experimental Oncology/Unit of Urology
Division of Urology
Department of Urology
Department of Urology and Andrology
Urology Unit
Department of Surgery
Department of Urology
Department of Urology
Department of Urology
Department of Urology
Department of Mechanical Engineering
Department of Surgical Sciences
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