New research shows combining two screening methods -- mammogram and ultrasound -- can increase the accuracy rate of finding breast cancer.

Dr. Wendie Berg, a radiologist with Johns Hopkins Medical Center, led a team of researchers who analyzed just how effective a breast ultrasound can be.

With a mammogram, cancer can be detected more easily in fatty breast tissue than in denser breast tissue. Dense breast tissue appears whiter on a mammogram so details can be difficult to discern.

Dr. Berg's team recruited more than 2,000 women. Each had dense breast tissue, were at high risk for breast cancer and each underwent both a mammography and an ultrasound.

"We found that overall mammography did pretty well, but it did miss a large number of cancers," said Dr. Berg. "Only half of the cancers present were actually seen on mammography."

In total, 40 women were diagnosed with cancer and 20 of those cancers were found with mammography. When ultrasound was added, 12 more cancers were revealed.

Only eight cancers went undetected by both mammography and ultrasound.

"The overall performance of mammography had an accuracy of 78 per cent," Dr. Berg said. "If we added ultrasound to that, the overall accuracy was much better at 91 per cent."

Dr. Paula Gordon, Clinical Professor of Radiology at the University of British Columbia, says mammography is still the gold standard for detecting breast cancer, even if it is not 100 per cent accurate.

"The accuracy of a mammogram is very much dependent on how dense a woman's normal breast tissue is," Dr. Gordon said.

"(Mammography) is the only test that has been proven in randomized control trials to reduce mortality from breast cancer."

Bonnie Ostrowski is glad she underwent a breast ultrasound.

She worried that a mammogram alone might not detect a cancer if she had one. She asked her doctor to also perform a screening ultrasound on each breast.

"I just felt that ultrasound would give a different view and I felt much more secure," she said.

In 2001, Ostrowski's mammogram did not find cancer, but her ultrasound did. The test showed a small irregular mass in her left breast -- and a biopsy confirmed it was invasive breast cancer.

Ostrowski is grateful she was able to have both a mammogram and a breast ultrasound. The screening tests caught her cancer early and she's been cancer free for seven years.

"I really do believe that the ultrasound did help save my life," she said.

With a report from CTV British Columbia's Dr. Rhonda Low