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Magnetic Resonance Mammography

Practice Essentials

Introduction to breast MRI

Breast MRI (magnetic resonance imaging), also known as magnetic resonance mammography, is a noninvasive technique for imaging the breasts. It creates high-quality images of the breasts and has better sensitivity and specificity for detection of breast cancer than the other currently available technologies. Breast MRI is also used in evaluation of integrity of breast implants.

(See the images below.)

MRI: A, Non-fat saturation T1 weighted image showi

MRI: A, Non-fat saturation T1 weighted image showing a T1 hypointense mass in the far lateral posterior aspect of the right breast. B, Fat-saturation T1 weighted dynamic (first pass) image shows the typical appearance of an invasive ductal carcinoma with intense early enhancement within 2 minutes of the injection of contrast material. The spiculated margin is characteristic of malignancy. The biopsy clip is seen as a signal void within the mass.

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MRI: A, Non-fat saturation T1 weighted image showi

MRI: A, Non-fat saturation T1 weighted image showing a T1 hypointense mass in the far lateral posterior aspect of the right breast. B, Fat-saturation T1 weighted dynamic (first pass) image shows the typical appearance of an invasive ductal carcinoma with intense early enhancement within 2 minutes of the injection of contrast material. The spiculated margin is characteristic of malignancy. The biopsy clip is seen as a signal void within the mass.

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3D thick-slab maximum intensity projection (MIP) M

3D thick-slab maximum intensity projection (MIP) MRI shows 4 lesions with ductal enhancement extending to the retroareolar region. Lesions A, B, and C were in a line, with lesion D lying higher and more central. All lesions and the retroareolar ductal enhancement were confirmed to be malignant at mastectomy.

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In ongoing research, including the EA1141 Trial, an abbreviated-protocol breast MRI is being investigated as a lower-cost method than traditional full diagnostic protocol breast MRI, while maintaining sensitivity and specificity for breast cancer.

See Breast Cancer for complete information on this topic.

Development of MRI-based breast examination

The breast was one of the first organs studied with MRI for the detection of cancer, albeit initially in vitro.
The breast was also the first organ in which the detection of invasive tumor neovascularity was highlighted through the application of rapid serial imaging after an injection of contrast agent.

With the clinical application of nonenhanced breast MRI, the value of T1-weighted (T1W) and T2-weighted (T2W) spin-echo imaging rapidly became clear, through the analysis of characteristics such as lesion morphology, signal intensity, and tissue relaxation times.

It also became clear that the T2 relaxation rates of benign tissues and malignant tissues overlap
and that in situ cancers could not be reliably detected at all. The development of a dedicated breast coil, rapid 2D gradient-echo (GRE) imaging, high field strength (>1T) magnets that enabled spectral fat-suppression, new methods of k-space filling to increase resolution and speed, and bolus injection of gadolinium dimeglumine created the technique of dynamic contrast-enhanced breast MRI. This technique showed an extremely high sensitivity for breast malignancy, higher than conventional methods of breast imaging.

Although dynamic contrast-enhanced breast MRI was initially limited to a single section location, it was soon modified with newly developed multisection, spoiled GRE sequences. This thin-section dynamic contrast-enhanced technique formed the foundation of modern breast MRI. MRI-guided breast biopsy and localization methods have been developed to investigate abnormal areas seen on breast MRI.

(See the image below.)

Typical parametric color mapping software used to

Typical parametric color mapping software used to map the rate of contrast enhancement on a series of dynamic images acquired at the same locations over a period of time. By arbitrary convention, red and yellow represents faster and more-intense enhancement, while blue and green represent slower and weaker enhancement.

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Prerequisites for the performance and interpretation of breast MRI

Breast MRI is a highly specialized diagnostic technique that complements clinical assessment and conventional imaging with mammography and ultrasound (US). It does not replace these techniques, except in certain unusual situations. In general, breast MRI should not be performed without conventional imaging performed first.

When breast MRI is performed for screening or evaluation of breast cancer, administration of an intravenous gadolinium-based contrast agent is a must. If the patient has a contraindication to gadolinium administration, breast MRI should not be performed for evaluation of breast cancer. Non-contrast MRI of the breast should only be performed for assessment of integrity of breast implants.

Breast MRI is best performed in a multidisciplinary setting with access to additional breast imaging, as well as close collaboration between the surgeon, radiologist, oncologist, and pathologist.

Radiologists experienced in MRI but without a strong knowledge of breast disease and diagnosis often have major difficulties with the interpretation of breast MRI studies. The radiologist interpreting breast MRI must (1) have a thorough understanding of breast pathology and diagnostic workup of breast diseases, (2) work closely with a breast surgeon and pathologist, (3) be experienced in the interpretation of mammograms and breast sonograms, and (4) be experienced in image-guided breast biopsy techniques.

Role of breast MRI in detection and evaluation of breast disease

Breast MRI is used as an adjunct to conventional mammographic assessment.

It provides additional information in the following ways:

Finding breast cancer not detected by other imaging modalities in women with increased risk.

Finding breast cancer not detected by other imaging modalities in women with dense breasts.

Finding additional disease in recently diagnosed breast cancer cases (multifocal, multicentric, or bilateral disease).

Finding an invasive component in ductal carcinoma in situ lesions.

Breast MRI relies on detection of abnormal enhancement caused by neoangiogenesis associated with malignancy. The increasing use of breast MRI has inevitably been accompanied by increased detection of incidental enhancing abnormalities that were not detected by conventional imaging. These apparent lesions may represent normal or dysplastic tissues, cyclic hormonal changes, benign tumors, or unexpected malignant foci. The nature of such foci must be clarified so that a cancer is not missed and small cancers are identified.

Three strategies are commonly used to diagnose these lesions: performing MRI-guided repeat US (second-look ultrasound), repeating breast MRI at another suitable time, or performing MRI-guided needle biopsy.

Indications for performing breast MRI

Breast MRI is costly, is not as widely available as mammography, and needs injection of contrast medium. Optimal MRI imaging of breasts is performed between days 7 and 14 of a woman’s menstrual cycle to avoid the confounding background parenchymal enhancement. It can give rise to a larger number of false positives leading to unnecessary biopsies. Therefore, there are guidelines for performing breast MRI.

There is not enough evidence to make a recommendation for or against yearly MRI screening for women who have a moderately increased risk of breast cancer (a lifetime risk of 15-20% according to risk-assessment tools that are based mainly on family history) or who may be at increased risk of breast cancer based on certain factors, such as (1) having a personal history of breast cancer, ductal carcinoma in situ (DCIS), lobular carcinoma in situ (LCIS), atypical ductal hyperplasia (ADH), or atypical lobular hyperplasia (ALH) or (2) having dense breasts (“extremely” or “heterogeneously” dense) as seen on a mammogram.

If MRI is used, it should be in addition to, not instead of, a screening mammogram. This is because although an MRI is a more sensitive test (it’s more likely to detect cancer than a mammogram), it may still miss some cancers that a mammogram would detect.

For most women at high risk, screening with MRI and mammograms should begin at age 30 years and continue for as long as a woman is in good health. However, because the evidence is limited about the best age at which to start screening, this decision should be based on shared decision-making between patients and their health care providers, taking into account personal circumstances and preferences.

Indications for breast MRI in a diagnostic setting include the following:

Evaluation of extent of disease in a patient with recently diagnosed breast cancer (multifocal or bilateral disease).

Evaluation of invasive lobular carcinoma.

Characterization of an indeterminate lesion after a full assessment with mammography, ultrasonography, and physical examination.

Detection of occult primary breast carcinoma in the presence of carcinoma in axillary lymph node or metastatic adenocarcinoma of unknown origin.

Monitoring of the response to neoadjuvant chemotherapy.

Evaluation in postoperative patients with positive margins.

(See the image below.)

Invasive ductal carcinoma detected with screening

Invasive ductal carcinoma detected with screening mammography. A, Detailed mammography shows this as a stellate mass with suspicious microcalcifications. However, no microcalcifications are seen extending to the nipple. B, MRI shows intense enhancement in the tumor and in an expanded duct, which extends to the nipple. The nipple enhancement is within normal limits. Histology confirmed ductal carcinoma in situ (DCIS) extending to, but not involving, the nipple and areola.

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Breast MRI Screening as an Adjunct to Mammography

The American Cancer Society (ACS) recommends annual MRI screening along with mammography, based on evidence from nonrandomized screening trials and observational studies, in women with the following risk factors

BRCA mutation

First-degree relative of BRCA carrier, but untested

Lifetime risk ∼20–25% or greater, as defined by BRCAPRO or other models that are largely dependent on family history

The ACS recommends annual MRI screening, based on expert consensus opinion that considers evidence of lifetime risk for breast cancer, in women with the following risk factors

Radiation to chest between age 10 and 30 years

Li-Fraumeni syndrome or first-degree relatives with the syndrome

Cowden and Bannayan-Riley-Ruvalcaba syndromes or first-degree relatives with those syndromes

The ACS found insufficient evidence to recommend for or against MRI screening in women with the following risk factors 

Lifetime risk 15–20%, as defined by BRCAPRO or other models that are largely dependent on family history

Lobular carcinoma in situ (LCIS) or atypical lobular hyperplasia (ALH)

Atypical ductal hyperplasia (ADH)

Heterogeneously or extremely dense breast on mammography

Personal history of breast cancer, including ductal carcinoma in situ (DCIS)

The ACS recommends against MRI screening (based on expert consensus opinion) in women at < 15% lifetime risk.

Finally, the ACS advises that screening decisions should be made on a case-by-case basis, as there may be particular factors to support MRI. Payment should not be a barrier.

Contraindications to performing breast MRI

Contraindications to breast MI include the following:

Patient’s inability to lie prone.

Marked kyphosis or kyphoscoliosis.

Marked obesity.

Extremely large breasts.

Severe claustrophobia.

Inability to use gadolinium-based contrast media (history of allergy to contrast media or pregnancy).

Other general contraindications to MRI.

Gadolinium-based contrast agents have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent.

Advantages of breast MRI

The advantages of breast MRI include the following:

No ionizing radiation.

Multiplanar capability.

Capability of imaging the entire breast volume and chest wall.

3-dimensional (3D) lesion mapping with techniques such as maximum intensity projection (MIP) slab 3D reconstruction.

Detection of occult, multifocal, or residual malignancy.

Accurate size estimation for invasive carcinoma.

Good spatial resolution.

Ability to image regional lymph nodes (axillary as well as internal mammary).

In a study by Wasif et al, MRI was found to be more accurate than ultrasonography or mammography in the determination of the size of breast cancer masses. Out of 61 lesions, MRI-based tumor size was within 1 cm of pathologic size in 44 (72%) tumors, more than 1 cm above pathologic size in 6 tumors, and more than 1 cm below pathologic size in 11 tumors.

Weinstein et al concluded that the addition of MRI to mammography in patients with a high risk of breast cancer has the greatest potential to detect additional, mammographically occult cancers. The investigators prospectively compared breast cancer detection of digital mammography (DM), whole-breast US (WBUS), and contrast-enhanced MRI in a high-risk screening population that previously screened negative with film screen mammography (FSM).

In the Weinstein study, the cancer yield by modality was evaluated, and 20 cancers were diagnosed in 18 patients (9 ductal carcinomas in situ and 11 invasive breast cancers). The overall cancer yield on a per-patient basis was 3% (18 of 609 patients). The cancer yield by modality was 1% for FSM (6 of 597 women), 1.2% for DM (7 of 569 women), 0.53% for WBUS (3 of 567 women), and 2.1% for MRI (12 of 571 women). Of the 20 cancers detected, some were detected on only one imaging modality (FSM, 1; DM, 3; WBUS, 1; MRI, 8).

Moy et al evaluated breast MRI in cases in which mammographic or ultrasonographic findings were inconclusive, and they found that MRI had a sensitivity of 100% and a significantly higher specificity than mammography (91.7% vs 80.7%, respectively). MRI also had greater positive predictive value (40% vs 8.7%) and overall accuracy (92.2% vs 78.3%).

(See the images below.)

Spot compression MLO view showing two masses in th

Spot compression MLO view showing two masses in the inframammary fold region.

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Same patient as in the previous mammogram: Reconst

Same patient as in the previous mammogram: Reconstructed T1 weighted fat-saturation sagittal image of right breast shows the two masses seen on the mammogram and a third mass more superiorly and posteriorly. The inferior-most mass shows a signal void from the biopsy clip.

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Same patient as in the previous MRI: Axial T1 fat-

Same patient as in the previous MRI: Axial T1 fat-saturated dynamic contrast-enhanced images show an enlarged right internal mammary lymph node.

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Same patient as in the previous MRI: PET-CT showin

Same patient as in the previous MRI: PET-CT showing intense hypermetabolic activity in a right internal mammary lymph node.

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Limitations of breast MRI

There are several factors that limit the widespread use of breast MRI, such as the following:

High equipment cost.

Limited scanner availability.

Need for the injection of a contrast agent.

No standard technique.

Poor throughput compared to that of US or mammography.

Large number of images.

Relatively long learning curve for interpretation.

False-positive enhancement in some benign tissues (limited specificity).

Variable enhancement of in situ carcinoma.

An incidence of slowly or poorly enhancing invasive carcinomas of about 5%.

Breast MRI and mastectomy

There has been concern that because breast MRI has greater sensitivity in cancer detection than mammography and US, its increased use will lead to an increased rate of mastectomy in women with early stage breast cancer. However, Dang et al found that from 2003 to 2007, although the annual number of breast MRI scans ordered by their institution rose from 68 to 358, the percentage of women who underwent mastectomy did not change over that period.

Differential diagnosis of lesions seen with breast MRI

If early rapid enhancement due to neovascularity were unique to malignant tissues, breast MRI would be the standard in clinical practice today. Unfortunately, such enhancement is not specific, and several benign conditions may enhance in a fashion similar to cancer. Conversely, a small percentage of malignancies either enhance identically to benign breast parenchyma or, rarely, do not enhance at all.

Benign pathologies that may mimic malignant enhancement include the following (false positive):

Cyclical physiologic parenchymal enhancement


Sclerosing adenosis

Florid epithelial hyperplasia

Lobular carcinoma in situ


Fat necrosis

Posttreatment scarring and/or granulation tissue

Intraductal papilloma

Radial scar and/or complex sclerosing lesion

Silicone granuloma

Malignancies that may show benign-type enhancement include the following (false negative):


Highly scirrhous invasive ductal carcinoma (IDC)

Invasive lobular carcinoma

Mucinous carcinoma

Papillary carcinoma

Tubular carcinoma

MRI-guided ultrasonography (second-look US)

When a suspicious finding is seen on breast MRI, high-resolution targeted US is performed to detect and evaluate the lesion, as well as to provide guidance for biopsy as needed. It is frequently possible to perform an ultrasound-guided biopsy instead of a more expensive and time-consuming MR-guided biopsy. However, one should be careful, because a malignant lesion detected by MRI may be subtle and less specific in appearance on US; therefore, careful ultrasound scanning is required.

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