Breast CT, an investigational technology for early breast cancer detection, may be better than mammography at detecting breast lesions and is much more comfortable for women, UC Davis researchers reported Dec. 2 at the annual meeting of the Radiological Society of North America in Chicago.

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

She presented preliminary results from the first 21 patients enrolled in a 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 plans to evaluate about 190 patients, all with mammograms judged suspicious or highly suspicious for cancer, and in whom needle biopsies are warranted. Prior to the 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 Chicago meeting, Lindfors reported that lesions seen on mammography were also seen on breast CT in 19 of the first 21 cases. The unseen lesions were benign; one was in a very large breast, while 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 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.

In mammography, the breast is squeezed between two plates. Breast CT requires no such compression, and patients in the trial are asked to compare the two procedures on comfort scale of 1 to 10, with 1 indicating that breast CT is "much worse" than mammography and 10 indicating that breast CT is "much more comfortable." The first 21 patients gave breast CT an average score of 8.

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

UC Davis radiology Professor John Boone developed the breast CT prototype 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. Project funding of $6 million came from the California Breast Cancer Research Program, the National Cancer Institute and the National Institute for Biomedical Imaging and Bioengineering.

Computed tomography is used to scan brains, lungs, abdomens and pelvises. But imaging experts long ago labeled CT impractical for breast cancer screening, assuming that breast CT 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 the use of standard CT machines, which would require the scanning of the breast and entire chest at the same time. When he recalculated radiation doses based on scanning the breast alone, he found that CT imaging would use no more radiation than mammography.