Contrast-Enhanced Magnetic Resonance Imaging (MRI):
What is it? Contrast-enhanced magnetic resonance imaging (Breast MRI) is a noninvasive medical test that uses very strong magnets and pulses of radio waves to manipulate natural magnetic properties in the body. When used together with gadolinium-based intravenous contrast (known as a contrast-enhanced MRI), MRI looks at both structure and blood flow; cancerous tumors (Fig. 12) usually have increased or abnormal blood flow.
Figure 12. Contrast-Enhanced Breast MRI Showing Cancer. Axial MRI image of the right breast obtained after contrast injection (and after computer subtraction of non-enhanced images) in this 48-year-old woman (same patient as in Figure 6) shows irregular spiculated enhancing (white) mass (arrow) due to grade 2 invasive ductal carcinoma with DCIS.
How it works: Breast MRI requires a contrast agent that is administered intravenously. During an MRI exam, a patient lies face down and the breasts are positioned into two holes of a “coil” (the imaging device) (Fig. 13 & Fig. 14). The MRI scanner makes loud noises while imaging. The usual breast MRI examination takes about 30 to 40 minutes.
Figure 13. & Fig. 14 “Coil” and supports used to image the breasts for MRI. The patient lies face down with her head in the cushioned support and her arms raised. The breasts are placed in the rectangular openings (arrows). The patient is then moved into the tunnel of the scanner for imaging with the head facing out.
Benefits: Contrast-enhanced breast MRI reveals at least 10 additional cancers per thousand women screened after mammography, even when both mammography and ultrasound have been performed. MRI is very sensitive and is recommended every year for women who are at high risk for breast cancer.
Considerations: A contrast-enhanced Breast MRI is a sensitive test and will find more areas of concern than either a mammogram or ultrasound. Some of those “finds” will be cancer, but the majority will not (known as a “false positive”). It is important to have the examination performed at a facility that performs correlation with mammography and that has the ability to perform MRI-guided breast biopsy or has a formal arrangement with a facility which will do this; any facility accredited in breast MRI by the American College of Radiology will meet these requirements.
Not all patients can tolerate a contrast agent and it may pose a risk for women with kidney disease. Some women find claustrophobia an issue (as exam time is spent in an enclosed tube). This position can be difficult to keep for some patients with neck problems, obesity or breathing issues. Also, MRI cannot be performed in women who have certain metal implants such as pacemakers and is not recommended if the patient is pregnant. Data are emerging* showing there can be accumulation of gadolinium in parts of the brain in patients who have multiple contrast-enhanced MRI studies; the importance of this finding is unknown, and this appears to be an issue only with certain types of contrast agents**. To reduce normal hormonal changes in the breast, screening MRI is best performed from day 7-10 of the menstrual cycle.
A last consideration for MRI currently is its high cost, which is not always covered by insurance. A lower cost “fast” MRI has been developed which may take less than 10 minutes, but its availability is still quite limited. If MRI screening has been performed, there is no added benefit to ultrasound screening, though ultrasound is sometimes performed to guide biopsy of suspicious masses seen on MRI.
*McDonald RJ, McDonald JS, Kallmes DF, et al. (2015). Intracranial gadolinium deposition after contrast-enhanced MR imaging. Radiology. Retrieved from: http://dx.doi.org/10.1148/radiol.15150025
*Radbruch A, Weberling LD, Kieslich PJ, et al. (2015) Gadolinium retention in the dentate nucleus and globus pallidus is dependent on the class of contrast agent. Radiology. Retrieved from: pubs.rsna.org/doi/abs/10.1148/radiol.2015150337
**Early studies suggest that "linear” contrast agents accumulate in the brain whereas “macrocyclic” agents do not, though further study is needed. Linear agents include gadopentetate dimeglumine [Magnevist), gadodiamide [Omniscan], and gadoversetamide [OptiMARK]). Macrocyclic agents include gadoterate meglumine [Dotarem], gadobutrol [Gadavist], and gadoteridol [ProHance]).
**Chou CP, Lewin JM, Chiang CL, et al. Clinical evaluation of contrast-enhanced digital mammography and contrast enhanced tomosynthesis--Comparison to contrast-enhanced breast MRI. Eur J Radiol. 2015;84(12):2501-8.