Chemical decomposition of urinary stones during holmium-laser lithotripsy: II. Evidence for photothermal breakdown

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

doi:10.1117/12.350022

14 June 1999 Chemical decomposition of urinary stones during holmium-laser lithotripsy: II. Evidence for photothermal breakdown

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

Author Affiliations +

Proceedings Volume 3601, Laser-Tissue Interaction X: Photochemical, Photothermal, and Photomechanical; (1999) https://doi.org/10.1117/12.350022
Event: BiOS '99 International Biomedical Optics Symposium, 1999, San Jose, CA, United States

Abstract

Because of the greater than or equal to 250 microsecond 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. 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 (cf. part I). The mass- loss of desiccated calcium oxalate monohydrate (COM) stones exposed to 150 J from the Ho:YAG laser in air was 40 plus or minus 12 mg (mean plus or minus 1 s.d.); for hydrated stones in air was 25 plus or minus 9 mg; and for hydrated stones in water was 17 plus or minus 3 mg, p less than .001. These differences indicate that direct absorption of the laser radiation by the stone is required for the most efficient ablation. Lowering the initial temperature of COM or cystine stones also reduced the stone mass-loss following 20 J of delivered laser energy: 2.2 plus or minus 1.1 mg vs 5.2 plus or minus 1.6 mg for COM stones (-80 vs 23 degrees Celsius), and 0.8 plus or minus 0.4 mg vs 2.2 plus or minus 1.1 mg for cystine stones (-80 vs 23 degrees Celsius), p less than or equal to .05. Finally, chemical analysis of the laser-induced stone fragments revealed the presence of thermal breakdown products: CaCO₃ from COM; free sulfur and cysteine from cystine; Ca₂O₇P₂ from calcium hydorgen phosphate dihydrate, and cyanide from uric acid.

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Randolph D. Glickman, Joel M. H. Teichman M.D., George J. Vassar, Susan T. Weintraub, Kin Foong Chan, T. Joshua Pfefer, and Ashley J. Welch "Chemical decomposition of urinary stones during holmium-laser lithotripsy: II. Evidence for photothermal breakdown", Proc. SPIE 3601, Laser-Tissue Interaction X: Photochemical, Photothermal, and Photomechanical, (14 June 1999); https://doi.org/10.1117/12.350022

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