Holmium:YAG lithotripsy: Photothermal mechanism

George J. Vassar, Kin F. Chan, Joel M H Teichman, Randolph D. Glickman, Susan T. Weintraub, T. Joshua Pfefer, Ashley J. Welch

Research output: Contribution to journalArticle

153 Scopus citations

Abstract

Objective: A series of experiments were conducted to test the hypothesis that the mechanism of holmium:YAG lithotripsy is photothermal. Methods and Results: To show that holmium:YAG lithotripsy requires direct absorption of optical energy, stone loss was compared for 150 J Ho:YAG lithotripsy of calcium oxalate monohydrate (COM) stones for hydrated stones irradiated in water (17 ± 3 mg) and hydrated stones irradiated in air (25 ± 9 mg) v dehydrated stones irradiated in air (40 ± 12 mg) (P < 0.001). To show that Ho:YAG lithotripsy occurs prior to vapor bubble collapse, the dynamics of lithotripsy in water and vapor bubble formation were documented with video flash photography. Holmium:YAG lithotripsy began at 60 μsec, prior to vapor bubble collapse. To show that Ho:YAG lithotripsy is fundamentally related to stone temperature, cystine, and COM mass loss was compared for stones initially at room temperature (~ 23°C) v frozen stones ablated within 2 minutes after removal from the freezer. Cystine and COM mass losses were greater for stones starting at room temperature than cold (P ≤ 0.05). To show that Ho:YAG lithotripsy involves a thermochemical reaction, composition analysis was done before and after lithotripsy. Postlithotripsy, COM yielded calcium carbonate; cystine yielded cysteine and free sulfur; calcium hydrogen phosphate dihydrate yielded calcium pyrophosphate; magnesium ammonium phosphate yielded ammonium carbonate and magnesium carbonate; and uric acid yielded cyanide. To show that Ho:YAG lithotripsy does not create significant shockwaves, pressure transients were measured during lithotripsy using needle hydrophones. Peak pressures were < 2 bars. Conclusion: The primary mechanism of Ho:YAG lithotripsy is photothermal. There are no significant photoacoustic effects.

Original languageEnglish (US)
Pages (from-to)181-190
Number of pages10
JournalJournal of Endourology
Volume13
Issue number3
DOIs
StatePublished - Apr 1999

ASJC Scopus subject areas

  • Urology

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    Vassar, G. J., Chan, K. F., Teichman, J. M. H., Glickman, R. D., Weintraub, S. T., Pfefer, T. J., & Welch, A. J. (1999). Holmium:YAG lithotripsy: Photothermal mechanism. Journal of Endourology, 13(3), 181-190. https://doi.org/10.1089/end.1999.13.181