... With particles called bubbicles.

Two researhers at the University of Rochester (N.Y.) have applied for a patent on their "bubbicles" -- long-lasting, air-packed particles that enhance the utility of ultrasound for imaging liver tumors. This contrast agent consists of a synthetic, iodine-packed chemical called iodipamide ethyl ester, says physical chemist and inventor Michael R. Violante.

The porous bubbicle, 1 micrometer in diameter, resembles a hard, air-filled sponge. It holds its air much better than albumin-coated microspheres, according to Violante and co-inventor Kevin J. Parker.

As a result, the bubbicles--which are one-sixth the size of red blood cells -- stay in the blood until liver cells filter them out. Once in the liver, they "produce a tremendous increase in brightness," says Parker. Cancer cells in the liver do not absorb the bubbicles, so tumors appear much darker than surrounding tissue in ultrasound images.

Medisperse Limited Partnership in Rochester plans to develop and test the bubbicles for clinical applications, says Violante, the company's managing director. He thinks bubbicles may also prove useful for imaging blood flow in the body's deep-seated vessels.