Ultrasound makes blood stand out

Researchers from Brown University have found a way to use ultrasonic vibrations to take images of tumors.

The method involves using ultrasonic vibrations to image colloidal objects, which are spherical objects like particles and blood cells that are suspended in fluid.

The method could eventually be used for mammograms and to check for internal bleeding, according to the researchers.

The researchers' scheme involves shooting a beam of ultrasound through a region of the body to produce a radio frequency signal, which the researchers process to generate a spatial representation of colloidal objects.

The method produces a 500-fold contrast between blood and tissue, which makes it potentially useful for imaging tumors because tumors have more blood vessels than ordinary tissue, according to the researchers.

The fluid immediately surrounding a particle carries an electric charge opposite the charge on the surface of the particle. This keeps particles from clumping together. When sound waves strike colloidal objects, they cause the fluid around the particles to oscillate. The oscillating charge generates an alternating current, which produces radio frequency waves.

Traditional ultrasonic imaging, in contrast, uses changes in the speed of the sound waves caused by materials with different densities to image different types of tissue.

The method could be ready for practical use in mammograms in two to five years, according to the researchers. The work appeared in the November 29, 2004 issue of Applied Physics Letters.