Conebeam breast CT shines in calcification visualization

A conebeam breast CT scanner is producing exquisite 3D images and enabling visualization of tiny calcifications, but further work is needed to reduce radiation dose and improve system design.

"Conebeam CT is not ready for prime time yet, as some want to believe. But it's a great tool," said Dr. Posy Seifert, a managing partner at the Elizabeth Wende Breast Clinic in Rochester, NY.

Seifert's clinic is participating in a multicenter trial of an investigational conebeam CT scanner developed at the University of Rochester. A commercial version of the scanner is set to be marketed for diagnostic purposes by Koning of Henrietta, NY.

The scanner features a horizontal gantry with a conebeam CT imaging chain. The gantry, which includes a flat-panel detector, is mounted under the patient table. The patient lies face down on the table and a single breast hangs freely through a table cut-out. The x-ray tube rotates around the breast, and a standard 10-second scan produces 300 projection images.

Unenhanced breast CT was equal to or better than digital mammography, according to a pilot study of 20 screening cases and nine cancer cases. Seifert presented results at the 2006 RSNA meeting. Conebeam CT proved powerful in displaying anatomy and was better in assessing breast density and more accurate at measuring tumor size. Breast coverage was at least as good with breast CT as with digital mammography. The results suggest conebeam CT did not improve specificity, and researchers believe contrast could help in this respect.

Because the scanner obtains tiny slices, resolution is very high and calcifications are well visualized. In contrast, breast MRI, another alternative study, takes much longer to perform and is not well suited for calcifications.

However, the radiation dose used to produce the conebeam CT images was twice as high as with a standard mammogram. Researchers are now working to reduce the dose without sacrificing image quality. More work is also needed to improve the ergonomic design of the CT table to accommodate women of different sizes, Seifert said.