Oxford scientists use high-intensity focused ultrasound to kill cancer cells

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Scientists at the University of Oxford have built a device to beam waves of ultrasound into the body, generating bubbles at a tumor site, which then pop and kill rogue cancer cells, according to BBC News. By harnessing the energy released when tissue is exposed to high intensity focused ultrasound (HIFU) waves, the researchers say they can provide faster and better targeted treatment.

The U.K. research team plans to apply its new, non-invasive technique using HIFU in clinical trials at the Churchill Hospital in Oxford to treat patients with kidney and liver tumors without surgery.

In HIFU, ultrasound waves from outside the human body are brought to a focus inside the body, causing intense local heating which kills cells—the same as burning a hole in paper by focusing sunlight through a magnifying glass, according Constantin Coussios, MD, from Oxford's Biomedical Ultrasonics and Biotherapy Laboratory (BUBL).

But the existing HIFU technique has two important limitations that are hindering its clinical uptake. First, it is very slow, taking up to five hours to treat a 10cm tumor, compared to the 45 minutes or so it takes for surgery. Secondly, clinicians are working in the dark, since the results can only be assessed after the treatment is over.

By harnessing the tiny bubbles that form in tissue when it is exposed to focused ultrasound, Coussios and his colleagues at BUBL found they could boost the heating effect by a factor of 6-10 compared with conventional HIFU treatment.

While bubbles are created spontaneously when ultrasound is focused on a target inside the body, these bubbles normally form and burst very quickly. To achieve the effect Coussios and his team want, he said they have to keep the tissue bubbling long enough to heat it beyond 45 C, the temperature threshold at which cells start to die.

Their solution is a machine that beams ultrasound waves into the body and also has a highly-tuned sensor at its center. The sensor can "hear" the tiny bubbles collapsing - a sound which is a thousand times too high for dogs, let alone humans.

The enhanced technique is based on a principle called inertial cavitation. "I like to call it the 'energy shovel', because it allows us to grab this energy and use it where it is needed, delivering it as heat," Coussios said.