Breast MRI

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Breast MRI is an examination used to clarify the results of other breast imaging studies (mammography and ultrasound). It is also used in patients who may be at high risk for cancer which may be undetected by other means. This would include patients who have a known cancer and are being examined for other potential sites of breast cancer. It is controversial whether to include patients who have a high genetic risk of cancer, but many practitioners feel that this is also a valid indication.

[edit] Overview

The examination is conducted with the patient prone on the MR scanner, with breasts suspended in a special receiving coil in the MR machine. Intravenous gadolinium containing contrast media is used. The examination takes about 20-30 minutes.

Cancers are visible as areas which enhance (become more white on the scan images) with contrast administration. Simply showing an area enhances is not adequate to diagnose a cancer, as many benign processes will show enhancement, including fibroadenomas, areas of inflammation, and areas of simple fibrosis. A combination of findings, including morphology of the area, size of the area of enhancement, and the kinetic behavior of the enhancement curve, are used to determine if an area is suspicious.

If a suspicious area is found, it may require biopsy. Usually, the patient will be sent for an additional ultrasound focusing on the precise area that was abnormal on the MR scan. If nothing is found, it may be necessary to perform the biopsy in the MR scanner, using the MR images as direction. (This is not done first because it is more time consuming and more difficult to do using MR that using Ultrasound. Therefore, if the lesion can be seen with ultrasound, it is preferable to use the ultrasound to perform the biopsy.)

[edit] Value

The value of MR is that it can see more cancers than mammography or ultrasound. In patients with one known breast cancer, about 15% of patients will have a second cancer in the same breast not recognizable with Ultrasound or mammography. About 7% will have a second cancer in the opposite breast not visible using the other modalities. There is some controversy as to the significance of these additional cancers. Some feel that they usually would not become invasive cancers and thus may be irrelevant to the patient's care. Most feel, however, that finding these additional sites of cancer is very important to knowing how to approach a particular patient's situation.