Ultrasound elastography sharpens real-time images of liver tumors

A high-energy form of ultrasound produces images of liver tumors that are more conspicuous than those from traditional ultrasound, according to results of a clinical study.

Researchers at Duke University's Pratt School of Engineering found that acoustic radiation force impulse (ARFI) ultrasound may improve on conventional B-mode ultrasound for screening patients at increased risk for liver cancers. It may also guide biopsy procedures and minimally invasive therapies aimed at destroying cancerous tissues found deep in the abdomen.

Results based on evaluation of 12 liver tumors in nine patients were reported in the Jan. 7 issue of Physics in Medicine and Biology. Under the guidance of radiologist Dr. Gregg Trahey, Brian Fahey, Ph.D., and colleagues found that ARFI either improved or produced equivalent boundary definition for suspicious liver mass when compared with B-mode ultrasound.

The mean contrast for suspected hepatocellular carcinomas was 7.5 dB (range: 3.1-11.9) in the ARFI images compared with 2.9 dB (range 1.5-4.2) for B-mode ultrasound. The mean contrast for metastases was 9.3 dB (range: 5.7-13.9) for ARFI compared with 3.1 dB (range: 1.2-5.2) for B-mode ultrasound.

First developed six years ago by Duke biomedical engineers Trahey and Kathy Nightingale, ARFI uses high-energy sound waves to push on tissues like sonic fingers. A tracking beam then captures the movement of the tissue, providing a measure of its elasticity or stiffness.

"To our knowledge, these are the first images of abdominal malignancies in humans that show tissue elasticity," said Trahey, a professor of biomedical engineering, radiology, and medical physics at Duke.

Preliminary findings described in Fahey's Ph.D. thesis led Siemens Medical Systems to pursue a product prototype that will combine traditional ultrasound with ARFI, he said.

In general, primary liver cancers are soft, while those that have spread from other organs are hard. ARFI may be able to tell the difference between hard and soft tumors, Trahey said.

"If borne out in further studies, [that discriminating ability] suggests that ARFI may be useful in guiding treatment decisions," he said.

Traditional ultrasound is now the guidance method of choice in many hospitals for procedures targeting the liver, kidneys, pancreas, and lymph nodes, Trahey said. A significant number of tumors are difficult to see with this method, however, requiring physicians to resort to alternatives such as CT and MRI, which add to the complexity and cost.

Collaborators on the study included Dr. Rendon Nelson, vice chair of radiology at Duke, along with David Bradway, Stephen Hsu and Douglas Dumont, all biomedical engineering graduate students at Pratt.

For more information from the Diagnostic Imaging archives:

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