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Our goal is an office-based, handheld ultrasound system to target, detach, break, and/or expel stones and stone fragments from the urinary collecting system to facilitate natural clearance. Repositioning of stones in humans (maximum 2.5 MPa, and 3-second bursts) and breaking of stones in a porcine model (maximum 50 cycles, 20 Hz repetition, 30 minutes, and 7 MPa peak negative pressure) have been demonstrated using the same 350-kHz probe. Repositioning in humans was conducted during surgery with a ureteroscope in the kidney to film stone movement. Independent video review confirmed stone movements (≥ 3 mm) in 15 of 16 kidneys (94%). No serious or unanticipated adverse events were reported. Experiments of burst wave lithotripsy (BWL) effectiveness on breaking human stones implanted in the porcine bladder and kidney demonstrated fragmentation of 7 of 7 stones on post mortem dissection. A 1-week survival study with the BWL exposures and 10 specific pathogen-free pigs, showed all findings were within normal limits on clinical pathology, hematology, and urinalysis. These results demonstrate that repositioning of stones with ultrasonic propulsion and breaking of stones with BWL are safe and effective. [ABSTRACT FROM AUTHOR]

This study was motivated by the desire to develop HIFU-based abscess treatments and addresses inactivation of E. coli in volumes up to 10 mL. Cells were treated with 1-MHz nonlinear pulsed HIFU (10 cycles, 2 kHz repetition frequency, +65/-12.8 MPa focal pressures, up to 65 MPa shock fronts). Surviving fraction [SF] was assessed by coliform assay demonstrating curvilinear inactivation kinetics. Reduction of SF to 50% required 2.5 or 6 min in 5 or 10 ml samples, respectively. On light microscopy, surviving cells from 5 min exposures appeared normal, with minimal debris; after 20 min, debris dominated. TEM images of insonated samples showed some undamaged cells, a few damaged but largely intact cells, and comminuted debris. Cellular damage associated with substantive but incomplete levels of inactivation can be subtle. This study demonstrates the feasibility of using pulsed HIFU for partial disinfection of liquid volumes. [ABSTRACT FROM AUTHOR]

Burst wave lithotripsy (BWL) is a new non-invasive method for stone comminution using bursts of sub-megahertz ultrasound. A porcine model of urolithiasis and techniques to implement BWL treatment has been developed to evaluate its effectiveness and acute safety. Six human calcium oxalate monohydrate stones (6–7 mm) were hydrated, weighed, and surgically implanted into the kidneys of three pigs. Transcutaneous stone treatments were performed with a BWL transducer coupled to the skin via an external water bath. Stone targeting and treatment monitoring were performed with a co-aligned ultrasound imaging probe. Treatment exposures were applied in three 10-minute intervals for each stone. If sustained cavitation in the parenchyma was observed by ultrasound imaging feedback, treatment was paused and the pressure amplitude was decreased for the remaining time. Peak negative focal pressures between 6.5 and 7 MPa were applied for all treatments. After treatment, stone fragments were removed from the kidneys. At least 50% of each stone was reduced to <2 mm fragments. 100% of four stones were reduced to <4 mm fragments. Magnetic resonance imaging showed minimal injury to the functional renal volume. This study demonstrated that BWL could be used to effectively fragment kidney stones with minimal injury. [ABSTRACT FROM AUTHOR]