Acoustical Society of America
ICA/ASA '98 Lay Language Papers

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Therapeutic Ultrasound: A Promising Future in Clinical Medicine

Lawrence Crum -
Michael Bailey, Peter Kaczkowski, Inder Makin, Pierre Mourad, Kirk Beach, Stephen Carter, Udo Schmiedl, Wayne Chandler, Roy Martin, Shahram Vaezy, George Keilman, Robin Cleveland, and Ronald Roy
University of Washington
Seattle, Washington 98105

Popular version of paper 2aBV2
Presented Tuesday morning, June 23, 1998
ICA/ASA '98, Seattle WA

When people think of ultrasound, they usually think of prenatal exams-fuzzy videotapes prized by new parents. Ultrasound has achieved great success in diagnostic imaging because it is safe, portable, and less expensive than other forms of medical imaging. A less well-known fact is that at much higher intensities, the same acoustic waves used in diagnostic imaging can be used therapeutically. High-intensity ultrasound can interact with tissue to generate heat, mechanical energy, and sometimes bubbles; and scientists have been working since the 1950's to use these effects in clinical settings. This talk will describe three areas of therapeutic ultrasound research currently taking place at the University of Washington: treating kidney stones, dissolving blood clots, and stopping bleeding inside the body without breaking the skin.

Shock Wave Lithotripsy

A type of therapeutic ultrasound in widespread clinical use today is extracorporeal shock wave lithotripsy (ESWL), commonly called "lithotripsy." ESWL is used to treat kidney stones, calcified particles that block the urinary tract and cause extreme pain and discomfort, and sometimes life-threatening complications. The procedure is relatively simple: a focused ultrasound shock wave is shot through water and into the patient's body to break up the stone into small pieces, which can then pass out of the body unhindered. The process is usually successful, much less invasive than surgery, and causes only minimal damage to the surrounding kidney tissue.

For all its success, however, scientists are only beginning to understand how ESWL actually breaks up kidney stones. The favored hypothesis at UW is that the shock wave creates tiny bubbles inside the stone which grow and collapse violently to break the stone apart. We will present some results that support the role of these bubbles in lithotripsy.

Ultrasound-Enhanced Drug Delivery

Ultrasound has also proven useful in a much different clinical application. Thrombi, or blood clots, can form in veins of patients with poor circulation. These clots are dangerous not only because they can block circulation, but because parts of them can break off, get stuck in smaller vessels, and cause strokes and heart attacks. Drugs called thrombolytics, which are normally given to break up these clots, are made dramatically more effective when low-intensity ultrasound is applied to the clot during their application. Once again, however, scientists are not sure why ultrasound helps, and we are doing experiments to determine the mechanism of ultrasound-enhanced thrombolysis and to optimize the treatment to break up clots quickly and effectively.

Acoustic Hemostasis

It turns out that ultrasound can be used not only to break up blood clots, but to form them. UW has been given a research grant to explore using high intensity focused ultrasound (HIFU) to stop internal bleeding non-invasively. The benefits of such a therapy would be enormous: trauma patients could be treated without the need for the sterile environment of an operating room and without the danger of infection normally associated with surgery. However, the problem has may facets: we have to determine whether a patient has internal bleeding, find the bleeding site, figure out how to use HIFU to stop the bleeding, and monitor the therapy so that the bleeding is stopped and the surrounding tissues are unharmed. So far, we have developed a method for identifying patients with internal bleeding, and tested the use of HIFU in the surgery room to stop bleeding in organs and vessels. Both of these experiments have been very successful, and will be presented along with other ongoing research in the acoustic hemostasis project.

Special thanks to Susannah Bloch, University of Washington in the preparation of this lay paper

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