CT scanning may replace painful mammography

Computed tomography (CT), sometimes called CAT scanning, is commonly used to scan brains, lungs, abdomens and pelvises. Until now it has been dismissed as a tool for breast cancer screening because of the level of radiation it was assumed to be needed for the work.

That assumption is being proved false by clinical testing presently being conducted at the University of California at Davis. A modified CT scanner is the first to reach the clinical testing stage since a prototype was tested in the 1970s and dismissed as impractical.

The machine's developer, John M. Boone, UC Davis professor of radiology and biomedical engineering, worked in collaboration with Karen K Lindfors and J. Anthony Seibert, UC Davis radiology professors and Thomas R. Nelson, UC San Diego radiology professor.

Understanding was that estimates about radiation doses for breast CT were based on use of standard machines which would require the breast and entire chest to be scanned as a unit. Recalculating radiation doses based on scanning the breast alone, Dr. Boone found that CT imaging would use no more radiation than mammography.

The breast CT scanner developed makes use of a state-of-the-art digital x-ray detector, coupled with a compact x-ray tube in a cone beam CT geometry. Where mammography results in two orthogonal images of each breast, the dedicated breast CT scanner will result in 100 to 160 CT images of each breast.

Unlike mammography in which the breast is squeezed between two plates, there is no breast compression with the CT machine. The patient lies face down on a padded table that has a circular opening, through which the patient laces one breast at a time. A CT machine beneath the table scans each breast. The screening takes about 17 seconds per breast.

Although work is being done on developing breast CT scanners at the Universities of Rochester and Massachusetts as well as Duke University, this is the first machine to reach the clinical testing stage.

The UC Davis project was funded by $6 million in grants from the California Breast Cancer Research Program, the National Cancer Institute and the National Institute for Biomedical Imaging and Bioengineering.