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Surgery by Sound - 2001-12-20

Highly focused high-intensity sound waves may some day replace the surgeon's knife in dealing with internal bleeding or treating cancerous tumors.

If rescue personnel had had the proper equipment to stop the internal bleeding in her hidden wounds, Princess Diana of England might have been saved from the deadly injuries she sustained in an automobile crash in a Paris tunnel.

And that's exactly what Dr. Shahram Vaezy, of the Center for Industrial and Medical Ultrasound at the University of Washington, Seattle, and his colleagues are working to develop. Their device that would detect and stop internal bleeding by cauterizing sealing the blood vessels with high frequency, sharply focused ultrasound.

Dr. Vaezy said, "The ultrasound waves are generated by a crystal that converts electricity. We use a crystal that can handle high current. It looks like a disk of about 10 centimeter in diameter that would be placed over the skin. There would be an imaging device, perhaps an ultrasound imaging device attached, which would then image the bleeding area. Once we've identified the bleeding area, we could deliver the cauterizing energy to the bleeding site to stop the bleeding."

Low-intensity ultrasound currently is being used to obtain images of various organs of the body. It occurred to scientists that tissue that readily absorbs ultrasound at high frequencies could be heated if the high intensity were focused on a particular spot in the body. That heat, the reasoning went, could also cauterize a wound, or stop the bleeding.

Dr. Lawrence Crum, director of the University of Washington center, calls this process "image guided transcutaneous acoustic hemostasis by high density focused ultrasound." In plain language, that means using sound waves to stop bleeding without breaking the skin. Dr. Crum said, "One could envision that someone could use this on the battle field or in some emergency situation, like a car accident. We have performed several experiments on animals to demonstrate that it does work. And we are trying to reduce the weight of the device, make it more portable, and move toward human trials in the future."

Ultrasonic surgery works well in soft tissue, such as the abdomen. Bones are difficult for the ultrasound wave to penetrate but the researchers say they expect to find a way around that obstacle.

The technique also holds the promise of destroying tumors by sealing off the blood supply required for their nourishment. Dr. Peter Kaczkowski, senior engineer, explains. "Many young boys," he said, "have taken a magnifying glass and focused the sun onto a small spot. One can start a fire with such a device. The ultrasound devices that we use to generate high-intensity focused ultrasound operate in a very analogous way. It works just like a lens but [while] a lens focuses energy that comes from outside the lens, this dish is actually the source of the sound."

Depending on the site of the tumor, the procedure can be completely painless. Dr. Gail ter Haar, an English doctor, is treating tumors that are deep in the liver where there is no nerve without any anesthesia and the patients do not experience pain. If the tumor were just at the outside edges of the liver where there are nerves, then treatment without anesthesia would not be possible.

Seattle team leader Lawrence Crum says a principal benefit of ultrasonic surgery is that it could lead to completely non-invasive surgery. "Most of us consider surgery to involve use of a scalpel under anesthetic," he said, "in which the body is opened and the surgeon goes in and manipulates and does whatever he needs to do. In the case of ultrasound, because we use such a focused energy, the hope is that we can do this transcutaneously, that is through the skin without opening it up."

The earliest beneficiaries of ultrasound surgery are patients with prostate cancer. And, Dr. Crum says, clinical trials are also under way for the treatment of breast tumors, as well as cancers of the kidneys, ovaries and the liver.