A new diagnostic device which uses a dual-head gamma camera system to detect tiny breast tumours has been developed by scientists in the US.

The device that resembles a mammography unit has been put together by Michael O'Connor and colleagues at Mayo Clinic. It may prove to be a valuable complementary imaging technique to mammography, said science portal EurekAlert.

Molecular Breast Imaging, as the new technique is called, is sensitive enough to detect tumours less than 10 mm in diameter in 88 percent of cases where it is used, the researchers said.

Early findings from a comparison of the device with mammography show it can detect small cancers that were not found using the latter.

The scientists conducted clinical trials comparing the new gamma camera with mammography in 2,000 women who come to Mayo Clinic for routine screening. In the first 250 patients, the device detected four cancers - three of which were not visible on a mammogram.

"Our ultimate goal is to detect small cancers that may be inconspicuous or invisible on a mammogram for high-risk women with dense breasts," said O'Connor.

The device will just be slightly more expensive than a mammogram and will be more comfortable for women as less pressure is needed to image a breast, he added.

Said Stephen Phillips, co-author of the study: "We hope that our studies will eventually show our device to be almost as sensitive as magnetic resonance imaging (MRI), which is probably the best diagnostic test available to date, but is not widely used because of its expense."

Another researcher added: "Although these initial results are very exciting, we clearly need to image more patients to confirm the promise of the device."