"In this initial evaluation, breast CT images were subjectively found to be equivalent to and potentially better than standard mammography for the detection and evaluation of breast cancer," reported Karen Lindfors, professor of radiology at UC Davis School of Medicine and Medical Center.

Lindfors presented preliminary results from the first 21 patients enrolled in an ongoing Phase II trial of a breast CT prototype developed at UC Davis. The trial is designed to determine if breast CT can detect lesions as effectively as mammography. Researchers will evaluate about 190 patients in all. Women in the trial all have mammograms that are suspicious or highly suspicious for cancer and warrant a needle biopsy.

Prior to the needle biopsy, each volunteer undergoes breast CT. Lindfors and her colleagues then compare the breast CT studies with the mammograms and pathology reports. The comparison is subjective and nonblinded.

At the radiological society meeting, Lindfors reported that lesions seen on mammography were also seen on breast CT in 19 of the first 21 cases. The two lesions not seen on breast CT were both benign. One of the two benign lesions was in a very large breast; the other was a low-density lesion.

Lindfors noted that breast CT modifications now in progress may improve the prototype machine's ability to scan very large breasts and to detect lower-density abnormalities.

"Initial impressions were favorable with respect to breast CT," she said. "However, it is apparent that refinements in patient positioning and improvements in viewing techniques and radiologist training will be required to optimally generate and interpret the breast CT image data."

If the current trial confirms that breast CT does as well as mammography, the next step will be a larger trial comparing the two technologies head to head. UC Davis researchers hope to show that breast CT can detect smaller tumors than mammography.

Patients in the current Phase II trial are also asked to compare the comfort of breast CT and mammography. The first 21 patients gave breast CT an average score of 8. (A score of one indicates breast CT is "much worse" than mammography and 10 indicates breast CT is "much more comfortable.")

A mammogram is an X-ray taken through all the layers of the breast at once. The breast CT prototype developed at UC Davis takes images of virtual "slices" of the breast — about 300 images per breast. Computers then assemble these images into highly detailed, three-dimensional pictures.

Unlike mammography, in which the breast is squeezed between two plates, the breast CT requires no breast compression. The patient lies face down on a padded table. The table has a circular opening in it, through which the patient places one breast at a time. A CT machine under the table rotates around each breast. Scanning takes about 17 seconds per breast.

The breast CT was developed by UC Davis radiology professor John Boone in collaboration with Lindfors, J. Anthony Seibert, also a radiology professor at UC Davis, and Thomas R. Nelson, a radiology professor at UC San Diego. The 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.

Computed tomography is used every day to scan brains, lungs, abdomens and pelvises. But imaging experts long ago dismissed CT as impractical for breast cancer screening, assuming it would require too much radiation.

Boone, a medical physicist who holds six scientific patents, decided to revisit the issue, recognizing that radiation-dose estimates for breast CT were based on use of standard CT machines, which would require the breast and entire chest to be scanned together. When Boone recalculated radiation doses based on scanning the breast alone, he found that CT imaging would use no more radiation than mammography.