2D vs. 3D Mammograms: Understanding the Differences

Finding breast cancer early allows for more effective treatment and leads to better outcomes. That’s why getting regular mammograms, the screening test designed to detect breast cancer, is so important.

“Mammograms are digital x-rays of the breast. They detect disruptions in the breast tissue or calcifications that may be early signs of breast cancer,” said Maxine S. Jochelson, MD, an American Society of Clinical Oncology (ASCO) expert and Director of Breast Imaging at Breastlink/RadNet in Los Angeles.

Initially, mammograms used two-dimensional (2D) technology to look for breast cancer. But now three-dimensional (3D) mammograms have become more common. Here’s what you need to know as you schedule and plan for your upcoming screening.

What are 2D and 3D mammograms?

A 2D mammogram is the conventional way to look at breast tissue. The machine takes 2 x-ray pictures of each breast. One is from top to bottom, while the other is from side to side. Together, these form a single, flat image of the breast.

A 3D mammogram is also known as digital breast tomosynthesis (DBT). The DBT machine moves in an arc over the breast. It takes many thin x-ray pictures of each breast from different angles. This creates more detailed images of the breast tissue.

“The 2D puts the whole breast tissue in one image, and small lesions may be hidden in the breast tissue,” said Dr. Jochelson. “With the 3D, you’re looking at tiny slices throughout the breast. This makes it easier to detect abnormalities that 2D mammography might miss.”

Either 2D or 3D mammograms are used to look for signs of breast cancer. In people who don’t have any breast symptoms or problems, these are called screening mammograms. If a doctor sees something unusual in a screening mammogram, they may order a more involved test called a diagnostic mammogram with extra images of the breast. In these cases, the doctor may recommend a breast ultrasound as well. Like screening mammograms, diagnostic mammograms can be done with 2D or 3D machines. Diagnostic mammograms are also used to take a closer look when someone has breast changes or symptoms, such as breast pain or a lump.

What are the differences between 2D and 3D mammograms?

Both 2D and 3D mammograms help find breast cancer early. But research shows that 3D mammograms can help clinicians spot cancer more easily than 2D mammograms.

Breast density can make a difference in what type of mammogram is recommended. A 3D mammogram provides a more detailed view of breast tissue in people with dense or non-dense breasts. Both dense breast tissue and cancer look white on a mammogram, and dense breast tissue may mask signs of cancer. Because 3D mammograms show layers of tissue more clearly, they can help clinicians tell the difference between dense tissue and cancer. Sometimes doctors recommend that people with extremely dense breasts have a different or additional test, such as an ultrasound.

“The goal is to find cancers early before they spread, and 3D imaging allows us to accomplish that more effectively,” said Dr. Jochelson.

3D mammograms can also help reduce the need for extra testing. When the results of a mammogram are abnormal or unclear, the patient may get called back for more tests. Sometimes those additional tests show that everything is fine. These instances are known as false positives. 3D mammograms result in fewer false positives than 2D mammograms. This can help patients avoid unnecessary stress and the potential costs of follow-up testing.

2D mammograms tend to be less expensive than 3D mammograms. They can be useful in certain situations, such as when less detailed images are needed after a biopsy. 2D mammograms also use a slightly lower dose of radiation than 3D. But the doses of radiation used in both 2D and 3D mammograms are considered safe.

While 3D mammograms have become more common, they may not be available at all breast imaging centers. When both types are available, the process for scheduling the tests may be different. 3D mammograms also may not be as widely covered by insurance as 2D mammograms. 3D coverage varies by state and insurance provider. You may have to pay an out-of-pocket fee for a 3D mammogram, even with insurance. Talk to your doctor and insurance provider to make sure you understand which type of mammogram is right for you, how to schedule it, and any potential costs you may have.

Questions to ask your care team

Routine breast cancer screening is essential. For more about the types of mammograms available to you, consider asking these questions:

• Do you know if I have dense or non-dense breasts?
• Which type of mammogram do you recommend for me, and why?
• What’s the difference between what a 2D and 3D mammogram will show?
• Can I get a 3D mammogram if I want one?
• How much of the cost does my insurance cover?
• How do I schedule my next mammogram?
• What should I expect to happen during my mammogram appointment?
• How long will it take to get the mammogram results?

Learn more about mammograms from the American Cancer Society:

• Breast Cancer Risk and Prevention
• American Cancer Society Recommendations for the Early Detection of Breast Cancer
• Mammograms
• Tips for Getting a Mammogram
• Understanding Radiation Risk from Imaging Tests
• Breast Density and Your Mammogram Report

Dr. Jochelson is an ASCO member.