Ultrasound 'eye' scans organs from within

Science News, Feb 23, 1991 by Wendy Gibbons

Ultrasound 'eye' scans organs from within

A pinhead-sized ultrasound device, threaded through body passages with a catheter, prvides inside views of anatomic cavities, depicting these hard-to-image regions in two and three dimensions, reports radiologist Barry B. Goldberg.

Using a television screen, Goldberg displayed his preliminary 3-D images publicly for the first time last week at the annual meeting of the American Association for the Advancement of Science in Washington, D.C.

The tiny ultrasound transducer, initially developed for detecting plaque buildup inside arteries, could help reveal abnormalities within a variety of passageways such as the ureter, fallopian tubes and bile ducts, Goldberg suggests. These inner recesses are difficult to picture with conventional ultrasound techniques, which use much larger transducers and which view body tissues from the outside looking in, he says.

"We see beyond the [tissue] surface," Goldberg says. "We are able to picture abnormalities that before were very difficult to see by any other methods."

In the January AMERICAN JOURNAL OF RADIOLOGY, he ad his co-workers at Thomas Jefferson University in Philadelphia reported using the novel device to obtain 2-D images from the inside of the ureter, the tube linking the bladder and kidneys. The images, they say, pinpointed nearby problem areas -- including kidney stones and a blood vessel pressing on the ureter -- not seen during examinations with an endoscope, an optical instrument that provides surface views when inserted into body passages. Goldberg speculates that 3-D versions of such images will prove even more useful than the 2-D pictures.

When the transducer reaches its target site in the body, it sends out sound waves and receives them as they bounce back from nearby tissue layers. The transducer rotates 360 degrees to create a series of 2-D cross sections. For a 3-D image, a computer combines successive cross sections, piling them up like slies of bread in a loaf.

Unlike magnetic resonance imaging or CAT scans, the ultrasound 'eyeball' could easily be inserted during surgery to depict abnormalities embedded within tissue, Goldberg says.

Eric vanSonnenberg, an ultrasound researcher at the University of California, San Diego, says 2-D imaging of tubes such as the ureter holds promise but needs more evaluation to compare its clinical potential with that of other approaches. As for 3-D imaging, "it may turn out to be useful," but practical applications remain speculative, he cautions.

Goldberg agrees that his experiments have yet to establish the clinical advantages of the new 3-D views, but he suggests the added dimensions might, for instance, help physicians assess a tumor's size and how deeply it has invaded adjacent tissue, improving their ability to make treatment decisions.