MRI of the breast is utilized in many ways. It is not indicated in every patient diagnosed with cancer, but can serve as an excellent tool in some situations. It is a terrific adjunct to mammography in patients without cancer who are simply at high risk.
How Does MRI Work?
MRI does not depend on ionizing radiation. Instead, while in the magnet, radio waves redirect hydrogen atoms that naturally exist within the body. As the hydrogen atoms return to their usual alignment, they emit energy that varies according to the type of body tissue. The MR scanner listens for this energy and creates a picture of the tissues scanned.
A computer then processes the signals and generates a series of images, each of which shows a thin slice of the body. The images can then be studied from different angles by the interpreting radiologist.
All women are at risk for developing breast cancer. As many as 1 in 8 will develop breast cancer in her lifetime. There are, however, those women, whose risk is much greater. These women have been found to benefit from more aggressive screening. While not preventing the occurrence of breast cancer, screening leads to earlier detection and in some cases greater cure rate.
Guidelines established by an expert panel in 2007 by the American Cancer Society for the implementation of screening breast MRI include:
Diagnostic breast MRI is commonly used in women diagnosed with breast cancer to evaluate the extent of disease before surgery and for contralateral (opposite breast) screening in newly diagnosed patients, in those presenting with axillary (lymph node) disease only and to monitor the response to neoadjuvant chemotherapy (chemotherapy given BEFORE surgery).
MR-Guided Core Biopsy
When a lesion is visible only on an MRI, and, felt to be either indeterminate or suspicious, a biopsy is sometimes necessary. Image-guided, minimally invasive procedures such as MR-guided breast biopsies are most often performed by a specially trained breast radiologist and performed in the Breast Imaging Department.
Breast biopsies are usually done on an outpatient basis.
In most cases, you will lie face down on a moveable exam table and the affected breast or breasts will be positioned into openings in the table. The MRI is performed in the same way it was when the diagnostic MRI was performed (with dye). Your breast will be compressed between two compression plates (similar to those used in a diagnostic MRI exam) one of which is marked with a grid structure. Using computer software, the radiologist measures the position of the lesion and calculates the position and depth of the needle placement.
A local anesthetic will be injected into the breast and a very small nick is made in the skin at the site where the biopsy needle is to be inserted.
The radiologist then inserts the needle, advances it to the location of the abnormality and MR imaging is performed to verify its position.
Tissue samples are then removed ususally with a vacuum assisted device so multiple biopsies can be performed in a short period of time without removing the needle. After this sampling, the needle will be removed. A small marker may be placed at the biopsy site so that it can be located in the future if necessary.
Once the biopsy is complete pressure will be applied to stop any bleeding and the opening in the skin is covered with a dressing. No sutures are needed.
A mammogram may be performed to confirm that the marker is in the proper position.
This procedure is usually completed within 45 minutes.