Abstract
Objectives
Holmium–YAG (Ho:YAG) laser lithotripsy is a multi-pulse treatment modality with stochastic effects on the fragmentation. In vitro investigation on the single-pulse-induced effects on fiber, repulsion as well as fragmentation was performed to identify potential impacts of different Ho:YAG laser pulse durations.
Materials and methods
A Ho:YAG laser system (Swiss LaserClast, EMS S.A., Nyon, Switzerland) with selectable long- or short-pulse mode was tested with regard to fiber burn back, the repulsion capacity using an underwater pendulum setup and single-pulse-induced fragmentation capacity using artificial (BEGO) stones. The laser parameters were chosen in accordance with clinical application modes (laser fiber: 365 and 200 µm; output power: 4, 6 and 10 W in different combinations of energy per pulse and repetition rate). Evaluation parameters were reduction in fiber length, pendulum deviation and topology of the crater.
Results
Using the long-pulse mode, the fiber burn back was nearly negligible, while in short-pulse mode, an increased burn back could be observed. The results of the pendulum test showed that the deviation induced by the momentum of short pulses was by factor 1.5–2 higher compared to longer pulses at identical energy per pulse settings. The ablation volumes induced by single pulses either in short-pulse or long-pulse mode did not differ significantly although different crater shapes appeared.
Conclusion
Reduced stone repulsion and reduced laser fiber burn back with longer laser pulses may result in a more convenient handling during clinical application and thus in an improved clinical outcome of laser lithotripsy.
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Acknowledgments
The authors would like to thank T. Kiris, D. Döring, J. Kusnetsova and S. Fiedler for technical assistance during the experiments. The authors would like to thank Thorlabs GmbH, Dachau/Munich, Germany, and the project Light4LIFE granted by Internationales Büro - BMBF for support.
Conflict of interest
The authors declare that they have no conflict of interest.
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The manuscript does not contain clinical studies or patient data.
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Appendix
Appendix
Both terms “retropulsion” and “repulsion” are used and mixed up in the available laser lithotripsy literature. According to the definition, the term “retropulsion” describes a situation of a person falling backwards while stopping a backward movement, e.g., suffering from Parkinson’s disease in neurology. In physics, “repulsion” is defined as the force that acts between objects tending to separate them. With regard to these definitions, it should be appropriate to use the term repulsion as it describes the situation in lithotripsy in a clear manner although the term “retropulsion” is more often used in urologic publications.
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Sroka, R., Pongratz, T., Scheib, G. et al. Impact of pulse duration on Ho:YAG laser lithotripsy: treatment aspects on the single-pulse level. World J Urol 33, 479–485 (2015). https://doi.org/10.1007/s00345-015-1504-9
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DOI: https://doi.org/10.1007/s00345-015-1504-9