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Frequency Threshold for Ablation During Holmium Laser Lithotripsy: How High Can You Go?
J Endourol. 2020 Oct; 34(10):1075-1081.JE

Abstract

Purpose:

We performed in vitro studies to assess the relationship of pulse frequency on stone ablation during contact laser lithotripsy and determine if there is a threshold after which its effect on lithotripsy is limited.

Methods:

BegoStones were fragmented using a Ho:YAG laser (P120 Moses) and a 230 μm fiber at 0.5 J on long pulse (LP) and Moses distance (MD) modes in contact with the stone. The relationship between the number of pulses (1-40 Hz) on stone crater volume was assessed using three-dimensional confocal microscopy and nonlinear-segmented regression. To simulate a painting technique, we assessed fragmentation (mg/second) at 20, 40, and 60 Hz, with the fiber moving at a speed of 1 and 3 mm/second, respectively. High-speed imaging was used to record ablation.

Results:

When the laser fiber was fixed, after 13.0 (LP) and 15.4 (MD) pulses, greater pulse frequency did not lead to a significant increase in stone crater volume. Fragmentation was greatest at higher frequencies and faster fiber speed. Increasing the frequency from 20 to 60 Hz at 3 mm/second increased fragmentation by 82% and 61% for LP and MD modes, respectively. Using high-speed data, if the laser fiber is moving at 1 mm/second, a hypothetical frequency threshold for ablation was calculated to be 52 and 61.6 Hz for LP and MD modes, respectively.

Conclusion:

Increasing the fiber speed increases stone ablation when using high frequency settings. When the fiber is fixed there is a threshold after which increasing the pulse frequency leads to minimal gain in ablation. The exact value for threshold when the fiber is moving needs further study. Our study serves to provide insight for parameter selection and safety of laser lithotripsy for dusting technique.

Authors+Show Affiliations

Department of Urology and University of Michigan, Ann Arbor, Michigan, USA.Department of Urology and University of Michigan, Ann Arbor, Michigan, USA.Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.Department of Urology and University of Michigan, Ann Arbor, Michigan, USA. Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.Department of Urology and University of Michigan, Ann Arbor, Michigan, USA.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

32483996

Citation

Aldoukhi, Ali H., et al. "Frequency Threshold for Ablation During Holmium Laser Lithotripsy: How High Can You Go?" Journal of Endourology, vol. 34, no. 10, 2020, pp. 1075-1081.
Aldoukhi AH, Black KM, Hall TL, et al. Frequency Threshold for Ablation During Holmium Laser Lithotripsy: How High Can You Go? J Endourol. 2020;34(10):1075-1081.
Aldoukhi, A. H., Black, K. M., Hall, T. L., Roberts, W. W., & Ghani, K. R. (2020). Frequency Threshold for Ablation During Holmium Laser Lithotripsy: How High Can You Go? Journal of Endourology, 34(10), 1075-1081. https://doi.org/10.1089/end.2020.0149
Aldoukhi AH, et al. Frequency Threshold for Ablation During Holmium Laser Lithotripsy: How High Can You Go. J Endourol. 2020;34(10):1075-1081. PubMed PMID: 32483996.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Frequency Threshold for Ablation During Holmium Laser Lithotripsy: How High Can You Go? AU - Aldoukhi,Ali H, AU - Black,Kristian M, AU - Hall,Timothy L, AU - Roberts,William W, AU - Ghani,Khurshid R, Y1 - 2020/07/20/ PY - 2020/6/3/pubmed PY - 2020/6/3/medline PY - 2020/6/3/entrez KW - Moses KW - dusting KW - frequency KW - holmium laser KW - kidney stone KW - lithotripsy SP - 1075 EP - 1081 JF - Journal of endourology JO - J Endourol VL - 34 IS - 10 N2 - Purpose: We performed in vitro studies to assess the relationship of pulse frequency on stone ablation during contact laser lithotripsy and determine if there is a threshold after which its effect on lithotripsy is limited. Methods: BegoStones were fragmented using a Ho:YAG laser (P120 Moses) and a 230 μm fiber at 0.5 J on long pulse (LP) and Moses distance (MD) modes in contact with the stone. The relationship between the number of pulses (1-40 Hz) on stone crater volume was assessed using three-dimensional confocal microscopy and nonlinear-segmented regression. To simulate a painting technique, we assessed fragmentation (mg/second) at 20, 40, and 60 Hz, with the fiber moving at a speed of 1 and 3 mm/second, respectively. High-speed imaging was used to record ablation. Results: When the laser fiber was fixed, after 13.0 (LP) and 15.4 (MD) pulses, greater pulse frequency did not lead to a significant increase in stone crater volume. Fragmentation was greatest at higher frequencies and faster fiber speed. Increasing the frequency from 20 to 60 Hz at 3 mm/second increased fragmentation by 82% and 61% for LP and MD modes, respectively. Using high-speed data, if the laser fiber is moving at 1 mm/second, a hypothetical frequency threshold for ablation was calculated to be 52 and 61.6 Hz for LP and MD modes, respectively. Conclusion: Increasing the fiber speed increases stone ablation when using high frequency settings. When the fiber is fixed there is a threshold after which increasing the pulse frequency leads to minimal gain in ablation. The exact value for threshold when the fiber is moving needs further study. Our study serves to provide insight for parameter selection and safety of laser lithotripsy for dusting technique. SN - 1557-900X UR - https://www.unboundmedicine.com/medline/citation/32483996/Frequency_Threshold_for_Ablation_During_Holmium_Laser_Lithotripsy:_How_High_Can_You_Go L2 - https://www.liebertpub.com/doi/10.1089/end.2020.0149?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -
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