New medical imaging is taking mammography from 2D to 3D, providing physicians with a better picture of cancer.

The main screening tool for breast cancer, one of the most common cancers among Canadian women, is currently 2D mammography, which takes two X-ray images of the flattened breast. However, the results are not always clear.

“On a mammogram, fat looks black and normal breast tissues (glandular and fibrous) are white,” explains Dr. Paula Gordon, Medical Director at B.C. Women’s Hospital Breast Health Program. “But cancer is also white.”

If a patient’s cancer is surrounded by normal tissue, it can be more difficult or impossible to detect using a 2D mammogram. Studies indicate that 2D mammography will miss cancers in approximately 2 out of every 10 patients.“It’s like looking for a snowman in a snowstorm,” Dr. Gordon says.

A better picture

New 3D mammography, also known as tomosynthesis, produces up to 15 X-ray photos of thin slices of the breast from different angles and digitally pieces them together to create a 3D image, similar to a CT scan or an MRI. 

“3D mammography lets us look at the breast in 1mm slices instead of looking at the whole breast in one single picture,” says Dr. Gordon. “That makes it easier to see some cancers that are hiding in the dense tissue that we might’ve missed on a 2D mammogram.”

Dr. Supriya Kulkarni, a medical imaging expert at the Princess Margaret Cancer Centre, has used 3D mammography for more than 3 years and has seen the difference it can make — especially since it can help spot cancers while they are still small. “For breast cancer, early detection is the best chance you can give to a woman for the best possible outcome,” says Dr. Kulkarni.

Fewer false alarms 

When using 2D mammography, normal tissues can be mistaken for cancerous lesions, resulting in patients being passed on for further testing — requiring more time from physicians, prolonging patient anxiety, and even subjecting them to unnecessary biopsies.

“It is definitely going to be the future of screening, it’s a win-win: finding more cancers and calling back fewer women.”

Since 3D mammography creates a more detailed image of the breast, studies indicate that a lot of these “false positives” have been reduced.

This technology also gives physicians a better idea of legitimate causes for concern. For instance, Dr. Kulkarni says that in some cases, while a 2D mammogram will show a vague density, the technique of 3D mammography will show this potentially malignant mass more clearly, making detection easier.

For the future

Health Canada has approved the use of 3D mammography as a diagnostic tool, and according to Dr. Kulkarni it is increasingly being seen in medical centres across the country.

Both experts agree that this technology is a step towards better cancer detection. “It is definitely going to be the future of screening,” says Dr. Gordon. “It’s a win-win: finding more cancers and calling back fewer women.”