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Journal of Biomedical Optics • Open Access

Femtosecond laser lithotripsy: feasibility and ablation mechanism

Paper Abstract

Light emitted from a femtosecond laser is capable of plasma-induced ablation of various materials. We tested the feasibility of utilizing femtosecond-pulsed laser radiation (λ=800 nm, 140 fs, 0.9 mJ/pulse) for ablation of urinary calculi. Ablation craters were observed in human calculi of greater than 90% calcium oxalate monohydrate (COM), cystine (CYST), or magnesium ammonium phosphate hexahydrate (MAPH). Largest crater volumes were achieved on CYST stones, among the most difficult stones to fragment using Holmium:YAG (Ho:YAG) lithotripsy. Diameter of debris was characterized using optical microscopy and found to be less than 20 µm, substantially smaller than that produced by long-pulsed Ho:YAG ablation. Stone retropulsion, monitored by a high-speed camera system with a spatial resolution of 15 µm, was negligible for stones with mass as small as 0.06 g. Peak shock wave pressures were less than 2 bars, measured by a polyvinylidene fluoride (PVDF) needle hydrophone. Ablation dynamics were visualized and characterized with pump-probe imaging and fast flash photography and correlated to shock wave pressures. Because femtosecond-pulsed laser ablates urinary calculi of soft and hard compositions, with micron-sized debris, negligible stone retropulsion, and small shock wave pressures, we conclude that the approach is a promising candidate technique for lithotripsy.

Paper Details

Date Published: 1 March 2010
PDF: 5 pages
J. Biomed. Opt. 15(2) 028001 doi: 10.1117/1.3368998
Published in: Journal of Biomedical Optics Volume 15, Issue 2
Show Author Affiliations
Jinze Qiu, The Univ. of Texas at Austin (United States)
Joel M. Teichman, St. Paul's Hospital (Canada)
Tianyi Wang, The Univ. of Texas at Austin (United States)
Joseph Neev
Randolph D. Glickman, The Univ. of Texas Health Science Ctr. at San Antonio (United States)
Kin Foong Chan
Thomas E. Milner, The Univ. of Texas at Austin (United States)

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