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Ultrasound Pops Bubbles, Marks Breast Tumors

September 20, 2010
Written by: , Filed in: Breast Imaging
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It’s a long way even from human trials, let alone clinical use, but a new technique using gas-filled microspheres and ultrasound could provide better marking of breast cancer tumors—and make patients happier.

The problem: mammograms often reveal tumors too small to be felt. Surgeons need to know the tumors’ precise locations. But X-rays can’t guide surgeons in real time. So radiologists insert guide wires or radioactive seeds before surgery (sometimes days in advance) to mark the tumors. Both markers have drawbacks, including patient discomfort or outright pain.

The solution: tiny spheres of silica filled with perfluoropentane, a gas that has been used in short-term contrast agents. The spheres preserve the gas until ultrasound both bursts the spheres and detects the gas. Radiologists can inject the bubbles precisely into tumor areas up to several days before surgery, using thin needles for minimum discomfort. Ultrasound scans can then reveal the bubbles’ positions in 3-D on the operating table.

“These little gas-filled microbubbles stick to human breast tissue for days and can be seen with ultrasound,” said William Trogler, PhD, professor of chemistry and biochemistry at the University of California, San Diego (UCSD), as quoted in a news release. “If doctors placed them in early-stage breast cancer, which is difficult to see during surgery, they could help surgeons remove all of it in the first operation.”

Radiologists, chemists, and surgeons made up the UCSD team. They published their results in the new journal MedChemComm.

The researchers said they think ultrasound pressure waves burst the microbubbles. “They’re thin, fragile balls of porous glass, like Christmas tree ornaments,” said Andrew Kummel, PhD, another UCSD professor of chemistry and biochemistry. “The shell is just one two-hundredth of the diameter of the ball. When it breaks, the gas squirts out. Doppler ultrasound detects that movement.”

The team also examined the use of smaller, nano-scale silica microbubbles. The study reports that those are too minuscule to remain in place but might drain from a cancerous site and help identify lymph nodes to which cancer cells might migrate.

The current research shows the feasibility of the technique in tissue samples. Animal tests are under way. Next come toxicology tests and, eventually, clinical trials in humans.

Related seminar: Breast Imaging and Digital Mammography

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