The short answer: Contrast-enhanced mammography (CEM) is a mammogram taken after an IV injection of iodine contrast dye. Each view uses two quick X-ray exposures, and software turns them into an image that shows where blood flow is high. The FDA first cleared the method in 2011, as an add-on test after mammography and ultrasound.
Cancers grow new blood vessels, so they tend to soak up contrast faster than normal tissue. CEM uses that fact to make suspicious areas light up. The low-energy image still works as a regular mammogram, so you get both kinds of information from one visit.
How does contrast-enhanced mammography work?
A 2021 state-of-the-art review in Radiology describes the method. Iodinated contrast goes into a vein to highlight tumor blood vessels. Then the machine takes dual-energy digital mammograms.
Each compression gives the radiologist two images:
- A low-energy image. It looks like a standard digital mammogram and still shows calcifications and masses.
- A recombined (iodine) image. Software subtracts the normal tissue and leaves the areas that took up contrast.
GE's original 510(k) summary explains that both exposures happen one right after the other, during a single breast compression. You do not get squeezed twice for each view.
What happens during the exam, step by step?
Protocols vary by center. This sequence follows the technique described in a 2024 literature review in Cancers:
- Screening questions. Staff ask about past contrast reactions, kidney disease, an overactive thyroid, pregnancy, and breastfeeding. The review lists these as reasons a woman may be excluded.
- IV line. A technologist places a small catheter, usually in your forearm.
- Contrast injection. The usual dose is 1.5 mL of contrast per kg of body weight, given at about 3 mL per second.
- A two-minute wait. The contrast needs time to reach the breasts.
- Imaging. Compression starts about 2 minutes after the injection. Both breasts are imaged in the usual top-down (CC) and side (MLO) views within the next 8 minutes.
- Observation. Staff watch for a contrast reaction. The review says everyone involved in CEM must know how to treat one.
From injection to the last image, the core of the exam takes about 10 minutes. Each view still needs one compression, the same as a standard mammogram.
Who is CEM used for?
The FDA clearance lists CEM as an adjunct "following mammography and ultrasound exams to localize a known or suspected lesion." In practice, the Radiology review reports these main uses:
- Problem solving. CEM improved accuracy over digital mammography and ultrasound in women with abnormal screening results or breast symptoms.
- Staging a new cancer. It approaches the accuracy of breast MRI for showing how far a known cancer extends before surgery.
- Checking chemotherapy response. It also approaches MRI accuracy for tracking response to chemotherapy given before surgery.
- Screening higher-risk women. The review called early trial results "encouraging." It is not a routine screening test for average-risk women.
Dense breasts are the most studied screening use. In the UK BRAID trial (Lancet, 2025), 9,361 women aged 50 to 70 had dense breasts and a negative mammogram. CEM found 19.2 cancers per 1,000 exams. Abbreviated MRI found 17.4, and automated whole-breast ultrasound found 4.2. The difference between CEM and abbreviated MRI was not significant. For background on density, read dense breasts explained.
What if I have a contrast allergy?
Reactions to modern iodinated contrast are uncommon. The ACR Manual on Contrast Media (2026 edition) puts allergic-like reactions at 0.6% overall and 0.04% for severe ones.
In BRAID, 2,035 women had CEM. There were 17 minor reactions (8.4 per 1,000), 6 moderate (2.9 per 1,000), and 1 severe (0.5 per 1,000). There were also 3 cases where contrast leaked out of the vein.
The ACR manual makes these points about allergy history:
- A past allergic-like reaction to iodinated contrast raises the risk of another one about 5-fold.
- A shellfish or povidone-iodine (Betadine) allergy is not a significant risk factor.
- Routine premedication for food, drug, or seasonal allergies, or asthma, is not recommended.
- If you reacted before and the same contrast class is needed, premedication with steroids may be considered.
Many breast centers simply offer breast MRI instead, which uses a different class of contrast (gadolinium).
Do you need a kidney test first?
Possibly. Iodinated contrast leaves the body through the kidneys. A 2020 joint consensus from the ACR and the National Kidney Foundation found that kidney injury risk from IV contrast "has been overstated" in older research.
That same statement recommends IV saline before contrast for people with acute kidney injury or an eGFR below 30 mL/min/1.73 m² who are not on dialysis. The ACR manual calls this a relative, not absolute, reason to avoid contrast. The manual lists a history of kidney disease as a reason to check kidney function first, and diabetes as an optional one.
The ACR manual also says metformin does not raise the risk of contrast kidney injury. Tell the staff you take it anyway, because your center may have its own rule.
How much radiation does CEM use?
A little more than a standard mammogram. A two-center study of 348 CEM exams found a mean dose of 4.90 mGy for a two-view exam of both breasts. That was about 30% higher than digital mammography. The low-energy images made up 64% to 77% of the total.
The Radiology review describes the added dose as slight. For a sense of scale with standard exams, see how much radiation a mammogram exposes you to.
How does CEM compare to breast MRI?
Both tests use contrast to show blood flow. CEM is faster and uses a mammography machine. The Radiology review notes it may cost less and widen access to this kind of imaging.
MRI uses no radiation. The 2024 Cancers review says MRI is still the first choice for high-risk patients, and CEM suits those who cannot have MRI. For a full comparison, read breast MRI instead of a mammogram. For more on MRI scans in general, visit mri.md.
The bottom line
Contrast-enhanced mammography adds an iodine dye injection and a second X-ray exposure to a familiar mammogram. It helps radiologists solve unclear findings, stage cancers, and screen some women with dense breasts. Ask about it if MRI is not an option for you. Tell the staff about past contrast reactions, kidney disease, pregnancy, and breastfeeding.
Last updated: November 2026. This article is for informational purposes only and does not constitute medical advice. Talk with your doctor or breast imaging center about whether contrast-enhanced mammography is right for you.