Science News for Students - Spring 2021

New ultrasound treatment kills off cancer cells

It spares healthy cells while taking out cancerous ones

Pasadena. Low-intensity ultrasound, he says, “may allow physicians to target cancer cells based on their unique physical and structural properties.” Any spillover of the energy should cause little harm to healthy tissue. The treatment sends out pulses of sound waves —energy—that have a frequency above 20,000 hertz (cycles per second). That’s too high for our ears to hear. (That’s also what makes it “ultra” sound.) Medical imaging relies on very short pulses of this low-intensity ultrasound. Doctors had already used high-intensity ultra- sound to kill cancer cells. These sound waves send lots of energy to a small, focused area. The waves vibrate water inside cells within that area. This causes the cells to heat up. A lot. Targeted cells and their neighbors can reach 65° Celsius (149° Fahrenheit) in just 20 seconds. This kills cancer cells. The down side: It kills healthy ones, too. Mittelstein’s team tried a different approach. Another Caltech lab had studied effects of low-

By Alison Pearce Stevens M

ost cancer treatments involve surgery, chemical poisons or toxic radiation. Because they tend to take out healthy cells along with cancer-

ous ones, these treatments can leave patients tired, hurting and more. So researchers are look- ing for new approaches that spare the healthy cells. One new idea would destroy cancer cells with ultrasound energy. Even this treatment, however, can sometimes damage healthy tissue. But a new development may help. It limits the ultrasound energy’s damage to only the cancer cells. Healthy cells should suffer little if any harm from it. It’s exciting, says David Mittelstein of his team’s findings. Mittelstein is a biomedical engineer at the California Institute of Technology, in

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20 SCIENCE NEWS FOR STUDENTS | Invention & Innovation