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Proceedings Paper

Photothermal ablation is the primary mechanism in holmium:YAG laser lithotripsy of urinary calculi
Author(s): Randolph D. Glickman; Joel M. H. Teichman; Nicole S. Corbin; George J. Vassar; Susan T. Weintraub; Kin Foong Chan; Ashley J. Welch
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Paper Abstract

Because of the >= 250 microsecond(s) pulsewidth emitted by the Ho:YAG laser used in clinical lithotripsy, it is unlikely that stress confinement occurs within the irradiated stones. Experimental data supports a thermal mechanism for Ho:YAG laser stone ablation. Previous work has shown that stone fragmentation occurs soon after the onset of the laser pulse, is uncorrelated to cavitation bubble formation or collapse, and is associated with low pressures. Moreover, lithotripsy proceeds fastest with desiccated stones in air (data based on laser ablation of calcium oxalate monohydrate stones), indicating that direct absorption of the laser radiation by the stone material is required for the most efficient ablation. Lowering the initial temperature of calculi reduces the stone mass-loss following 20 J of delivered laser energy: 2.2 +/- 1.1 mg vs 5.2 +/- 1.6 mg for calcium oxalate monohydrate (COM) stones (-80 vs 23 degree(s)C), and 0.8 +/- 0.4 mg vs 2.2 +/- 1.1 mg for cystine stones (-80 vs 23 degree(s)C), p <EQ 0.5. In all of the stone compositions examined, thermal breakdown products have been detected, e.g. CaCO3 from COM; free sulfur and cysteine from cystine; Ca2O7P2 from calcium hydrogen phosphate dihydrate, and cyanide and alloxan from uric acid. All of these observations are most consistent with a photothermal breakdown process induced by Ho:YAG laser lithotripsy.

Paper Details

Date Published: 17 September 1999
PDF: 9 pages
Proc. SPIE 3863, 1999 International Conference on Biomedical Optics, (17 September 1999); doi: 10.1117/12.364416
Show Author Affiliations
Randolph D. Glickman, Univ. of Texas Health Science Ctr. (United States)
Joel M. H. Teichman, Univ. of Texas Health Science Ctr. (United States)
Nicole S. Corbin, Univ. of Texas Health Science Ctr. (United States)
George J. Vassar, Univ. of Texas Health Science Ctr. (United States)
Susan T. Weintraub, Univ. of Texas Health Science Ctr. (United States)
Kin Foong Chan, Univ. of Texas/Austin (United States)
Ashley J. Welch, Univ. of Texas/Austin (United States)


Published in SPIE Proceedings Vol. 3863:
1999 International Conference on Biomedical Optics
Qingming Luo; Britton Chance; Lihong V. Wang; Steven L. Jacques, Editor(s)

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