Breast MRI: State of the Art

Abstract

reast MRI is an indispensable modality, along with mammography and US. Its main indications are staging of known cancer, screening for breast cancer in women at increased risk, and evaluation of response to neoadjuvant chemotherapy (1-3). As opposed to mammography and US, MRI is a functional technique. Heywang et al (4) and Kaiser and Zeitler (5) independently introduced this technique in the 1980s. Contrast material-enhanced MRI evaluates the permeability of blood vessels by using an intravenous contrast agent (gadolinium chelate) that shortens the local T1 time, leading to a higher signal on T1-weighted images (6). The underlying principle is that neoangiogenesis leads to formation of leaky vessels that allow for faster extravasation of contrast agents (7), thus leading to rapid local enhancement. Despite improvements in the technique of breast MRI, this principle is still the basis of all clinical MRI protocols. However, most MRI protocols nowadays are multiparametric (8,9). This review describes the current state of the art in breast MRI, with a focus on the major indications and the potential indication-based adaptations to the imaging protocol to maximize its value. Requirements for Breast MRI Breast MRI studies should be interpreted by radiologists with expertise in breast imaging, including mammographic and US studies, as these examinations are often complementary. Although empirical data on the learning curve for breast MRI are lacking, some studies showed improved performance of radiologists over time (10), and reporting breast MRI studies requires sufficient exposure to the technique. It is best practice to use a field strength of at least 1.5 T to acquire images at a sufficiently high spatial resolution (1-3). Utilization of a dedicated breast coil is mandatory to obtain images of diagnostic quality. Women lie in the prone position with the breasts hanging free in the recesses of the coil. This design allows the breast tissue to spread, which facilitates detection of abnormalities and prevents motion artifacts induced by respiration (11,12). A breast coil should have at least four channels, but modern designs

Can contrast-enhanced mammography replace dynamic contrast-enhanced MRI in the assessment of sonomammographic indeterminate breast lesions?

“…Dynamic contrast-enhanced (DCE)-MRI allows better characterization of lesions through morphologic and kinematic assessment after administration of contrast material [5].…”

Role of MRI to Assess Response to Neoadjuvant Therapy for Breast Cancer

“…Clinical breast exam, mammography, ultrasound, and magnetic resonance imaging (MRI) have been used to evaluate response. Of these, MRI has been found to be the most accurate method, [6][7][8] likely due to its combination of physiologic and morphologic information. A combination of clinical breast exam and imaging may be used to stage the tumor by assigning a category of the extent of disease for the tumor, regional lymph nodes, and distant metastases, as per the American Joint Committee on Cancer 9 (Tables 1-3).…”

The supplemental value of mammographic screening over breast MRI alone in BRCA2 mutation carriers

“…Breast MRI was performed in each center using local protocols that all met the requirements of currently accepted international guidelines [16], including at least three highresolution T1-weighted acquisitions obtained before, early (90s), and late after (5-7 min) contrast administration. Dedicated analysis software (allowing for the creation of maximum intensity projections, signal intensity versus time curves, and color-coded overlays of enhancement patterns) and MR-guided biopsy tools were available in all centers.…”