Vibration imaging: sounding out tumors.

Vibration imaging: Sounding out tumors

Two researchers are tooting their own horn to detect cancerous tumors. The new technique, called doppler vibration imaging, is the first to use a horn's low-frequency sound waves to create vibrations that distinguish between hard and soft tissues, they say. Malignant tumors are more rigid and vibrate less rapidly than surrounding healthy tissues, offering a potentially useful diagnostic clue.

Tumors embedded in soft tissues such as the prostate, breast, liver and spleen often escape early detection because they can't be seen or felt, says Kevin J. Parker, who developed the imaging technique with Robert M. Lerner. The two University of Rochester scientists describe their work in the April ULTRASOUND IN MEDICINE AND BIOLOGY.

Like conventional ultrasound, doppler vibration uses sound waves to image targeted tissues in the body. Ultrasound, however, bombards tissues with inaudible sound waves at more than 20,000 hertz, and the echoes returning from tumors and healthy tissues can be identical, leaving the tumor undetected, Lerner says. Doppler vibration instead uses a speaker-like horn to generate whisper-soft sound waves at 200 hertz. A doppler device detects the resulting tissue motion, and a video screen displays a color "map" of the contrasting vibrational patterns.

Using the new method in rabbit livers and in human prostate and breast samples, the Rochester researchers say they have detected cancerous tumors that conventional ultrasound missed. They plan to conduct clinical trials and compare the method's sensitivity to that of other imaging systems in about a year. Lerner says the technique, if successful, would be much more affordable and more widely available than the magnetic resonance imaging sometimes used to detect prostate tumors or the CT scans often used to detect tumors in the liver and spleen.

"I'm convinced the principle [of the technique] works," says Daniel Rachlin of Stanford University, who has used doppler vibration imaging with synthetic tumor models. But the real test, he says, will come when researchers compare it with other imaging methods.