title: Recent developments in SWL physics research.
abstract: Two projects in our laboratory highlight some recent developments in shockwave lithotripsy (SWL) physics research. In the first project, we developed a prototype of a piezoelectric annular array (PEAA) shockwave generator that can be retrofitted on a Dornier HM-3 lithotripter for active control of cavitation during SWL. The PEAA generator, operating at 15 kV, produces a peak positive pressure of approximately 8 MPa with a -6-dB beam diameter of 5 mm. The shockwave generated by the PEAA was used to control and force the collapse of cavitation bubbles induced by a laboratory electrohydraulic shockwave lithotripter with a truncated HM-3 reflector. With optimal time delay between the lithotripter pulse and the PEAA-generated shockwave, the collapse of cavitation bubbles near the stone surface could be intensified, and the resultant stone fragmentation in vitro could be significantly improved. In the second project, high-speed shadowgraph imaging was used to visualize the dynamics of lithotripter-induced bubble oscillation in a vascular phantom. Compared with the free bubble oscillation in water, the expansion of cavitation bubble(s) produced in silicone tubes and a 200-microm cellulose hollow fiber by either a Nortech EHL or a Dornier XL-1 lithotripter was found to be significantly constrained. Rupture of the cellulose hollow fiber was observed consistently after about 20 shocks from the XL-1 lithotripter at an output voltage of 20 kV. These results confirm experimentally that SWL-induced cavitation in vivo can be significantly constrained by the surrounding tissue, and large intraluminal bubble expansions could cause rupture of capillaries and small blood vessels.
authors.affiliation: Department of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708-0300, USA. pz1@me1.egr.duke.edu
authors.forename: P
authors.initials: P
authors.lastname: Zhong
authors.forename: X
authors.initials: X
authors.lastname: Xi
authors.forename: S
authors.initials: S
authors.lastname: Zhu
authors.forename: F H
authors.initials: FH
authors.lastname: Cocks
authors.forename: G M
authors.initials: GM
authors.lastname: Preminger
mesh_terms: D006801:Humans; D007669:Kidney Calculi / Q000628:therapy; D008096:Lithotripsy / Q000639:trends*; D008863:Microspheres; D009991:Oscillometry; D010825:Physics / Q000639:trends*; D012106:Research