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Duryea AP et al, 2011: In vitro comminution of model renal calculi using histotripsy

Duryea A, Maxwell A, Roberts W, Xu Z, Hall T, Cain C
University of Michigan, Department of Biomedical Engineering, Ann Arbor, MI, USA


Abstract

Shock wave lithotripsy (SWL) suffers from the fact that it can produce residual stone fragments of significant size (>2 mm). Mechanistically, cavitation has been shown to play an important role in the reduction of such fragments to smaller debris. In this study, we assessed the feasibility of using cavitationally-based pulsed ultrasound therapy (histotripsy) to erode kidney stones. Previous work has shown that histotripsy is capable of mechanically fractionating soft tissue into fine, acellular debris. Here, we investigated the potential for translating this technology to renal calculi through the use of a commonly accepted stone model. Stone models were sonicated using a 1-MHz focused transducer, with 5-cycle pulses delivered at a rate of 1 kHz. Pulses having peak negative pressures ranging from 3 to 21 MPa were tested. Results indicate that histotripsy is capable of effectively eroding the stone model, achieving an average stone erosion rate of 26 mg/min at maximum treatment pressure; substantial stone erosion was only observed in the presence of a dense cavitational bubble cloud. Sequential sieving of residual stone fragments indicated that debris produced by histotripsy was smaller than 100 μm in size, and treatment monitoring showed that both the cavitational bubble cloud and model stone appear as hyperechoic regions on B-mode imaging. These preliminary results indicate that histotripsy shows promise in its use for stone comminution, and an optimized erosion process may provide a potential adjunct to conventional SWL procedures.

IEEE Trans Ultrason Ferroelectr Freq Control. 2011 May;58(5):971-80. doi: 10.1109/TUFFC.2011.1898
PMID: 21622053 [PubMed - in process]

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Comments 1

Peter Alken on Wednesday, 13 July 2011 13:52

Cavitation can erode solid material. This is known since hundred years (Silberrad O. Propeller erosion. Engineering 1912 33-35). In SWL it has positive and negative effects: stone fragmentation and tissue damage.

It seems that both effects can be used therapeutically. Known as Histotripsy, extracorporeally generated ultrasound producing intracorporeal cavitation has been applied to produce nonthermal tissue destruction in canine prostates. The surrounding tissue was not damaged. (Hempel CR, Hall TL, Cain CA, Fowlkes JB, Xu Z, Roberts WW. Histotripsy fractionation of prostate tissue: local effects and systemic response in a canine model. J Urol. 2011 Apr;185(4):1484-9.). The same group now presents in vivo work on artificial stones. Using the same technique stones were virtually pulverized into particles of ≤ 1/10 mm. Successful development into clinical use could end the story of CIRF.

Peter Alken

Cavitation can erode solid material. This is known since hundred years (Silberrad O. Propeller erosion. Engineering 1912 33-35). In SWL it has positive and negative effects: stone fragmentation and tissue damage. It seems that both effects can be used therapeutically. Known as Histotripsy, extracorporeally generated ultrasound producing intracorporeal cavitation has been applied to produce nonthermal tissue destruction in canine prostates. The surrounding tissue was not damaged. (Hempel CR, Hall TL, Cain CA, Fowlkes JB, Xu Z, Roberts WW. Histotripsy fractionation of prostate tissue: local effects and systemic response in a canine model. J Urol. 2011 Apr;185(4):1484-9.). The same group now presents in vivo work on artificial stones. Using the same technique stones were virtually pulverized into particles of ≤ 1/10 mm. Successful development into clinical use could end the story of CIRF. Peter Alken
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