Mechanical Tissue Destruction
The non-thermal effects of focused ultrasound can also be used for the precise destruction of tissue.
At high enough acoustic intensities with a short pulse duration, inertial cavitation will release a shockwave capable of destroying cell membranes and even liquefying or annihilating cells1,2. The use of inertial cavitation to mechanically destroy regions of tissue is known as histotripsy, and is usually the compounded effect of multiple shockwaves. This technique can be very precise, causing minimal damage to surrounding tissue, and the bubbles used in cavitation are easily visible with ultrasound imaging, enabling accurate targeting and monitoring3,4.
Clinically, histotripsy has a wide range of possible uses from cardiovascular disease5 to various types of cancer6. For very sensitive regions such as the brain, more research is needed to confirm the safety profile of treatment with histotripsy. Using injected microbubbles, to lower the threshold for inertial cavitation only at the target, may help reduce damage to adjacent tissue in the brain2,7.
For more information, see our April 2014 newsletter feature on histiotripsy.
 C.-J. Chen, H.-C. Hsu, W.-S. Chung, and H.-J. Yu, “Clinical experience with ultrasound-based real-time tracking lithotripsy in the single renal stone treatment.,” J. Endourol. / Endourol. Soc., vol. 23, no. 11, pp. 1811–1815, Nov. 2009.
 S. P. Wrenn, S. M. Dicker, E. F. Small, N. R. Dan, M. Mleczko, G. Schmitz, and P. A. Lewin, “Bursting bubbles and bilayers.,”Theranostics, vol. 2, no. 12, pp. 1140–1159, Dec. 2012.
 W. W. Roberts, T. L. Hall, K. Ives, J. S. Wolf Jr., J. B. Fowlkes, and C. A. Cain, “Pulsed cavitational ultrasound: A noninvasive technology for controlled tissue ablation (histotripsy) in the rabbit kidney,” J. Urol., vol. 175, no. 2, pp. 734–738, 2006.
 C. R. Hempel, T. L. Hall, C. A. Cain, J. B. Fowlkes, Z. Xu, and W. W. Roberts, “Histotripsy fractionation of prostate tissue: local effects and systemic response in a canine model.,” J. Urol., vol. 185, no. 4, pp. 1484–1489, Apr. 2011.
 Xu Z, Fowlkes JB, Rothman ED, Levin AM, Cain CA. Controlled ultrasound tissue erosion: the role of dynamic interaction between insonation and microbubble activity. J. Acoust. Soc. Am. 2005;117:424–35.
 Zhou Y-F. High intensity focused ultrasound in clinical tumor ablation. World J. Clin. Oncol. 2011;2:8–27.
 Kwan JJ, Graham S, Coussios CC. Inertial cavitation at the nanoscale. Proc. Meet. Acoust. 2013;19:075031.
Click here for additional references from PubMed.
Video courtesy of University of Michigan Engineering.