What is a MRI breast biopsy?
A breast MRI is used to assess the extent of breast cancer. It's also used to screen for breast cancer in women thought to have a high risk of the disease.
Your doctor may recommend a breast MRI if:
- A breast cancer diagnosis to find the extent of the cancer.
- You have a suspected leak or rupture of a breast implant
- You're at high risk of breast cancer, as calculated by risk tools that account for your family history and other risk factors
- You have very dense breast tissue, and mammograms didn't detect a prior breast cancer
- You have a history of precancerous breast changes — such as atypical hyperplasia or lobular carcinoma in situ — and a strong family history of breast cancer and dense breast tissue
- You have a hereditary breast cancer gene mutation, such as BRCA1 or BRCA2
- You had radiation treatments to your chest area before age 30
A breast MRI is intended to be used along with a mammogram or other breast-imaging test — not as a replacement for a mammogram. Although it's a sensitive test, a breast MRI can still miss some breast cancers that a mammogram will detect.
How does an MRI work?
Differing from x-ray and computed tomography (CT) exams, MRI does not use radiation. Instead, radio waves re-align hydrogen atoms that naturally exist within the body. This does not cause chemical changes in the tissues. As the hydrogen atoms return to their usual alignment, they emit different amounts of energy depending on the type of body tissue they are in. The scanner captures this energy and creates a picture using this information.
The magnetic field of the MRI unit is produced by passing an electric current through wire coils. Some tests require specific body coils which in some cases, are placed around the part of the body being imaged. These coils send and receive radio waves, producing signals that are detected by the machine. Specific body coils can direct the imaging on a direct body region. The electric current does not come in contact with the patient.
A computer processes the signals from the MRI machine and creates a series of images, each of which shows a thin slice of the body. These images can be studied from different angles by the radiologist.
MRI is able to tell the difference between diseased tissue and normal tissue better than x-ray, CT and ultrasound.
How is the procedure performed?
You will be positioned on the moveable exam table. Straps and bolsters may be used to help you stay still and maintain your position. Tests that use specific body coils capable of sending and receiving radio waves may be placed around or next to the area of the body being scanned. You will be placed into the magnet of the MRI unit. This looks like a large round opening, similar to a doughnut. The technologist will perform the exam while working at a computer outside of the room.
MRI exams generally include multiple runs (sequences), some of which may last several minutes. Depending on the type of exam and the equipment used, the entire exam is usually completed in 30 to 50 minutes.
If a contrast material is used, a doctor, nurse or technologist will insert an intravenous catheter (IV line) into a vein in your hand or arm that will be used to inject the contrast material. This often times is started after a series of initial scans.
When the exam is complete, you may be asked to wait while the radiologist checks the images in case more are needed.
What should I expect during and after the procedure?
Some patients find it uncomfortable to remain still for the duration of the exam. Others may feel closed-in (claustrophobic) while in the MRI scanner. The scanner can be noisy. It is normal for the area of your body being imaged to feel slightly warm. If it bothers you, tell the technologist. It is important that you remain perfectly still while the images are being taken. The technologist may give you instructions regarding on what you may need to do, such as taking in breaths. The machine will make loud tapping or thumping sounds which you will feel and hear. These are made when the coils that generate the radio waves are activated. You will be provided with earplugs and headphones to reduce the sounds made by the scanner. You may be able to relax between imaging sequences. However, you will be asked to keep the same position without moving as much as possible.
During the exam, you are usually alone in the exam room. The technologist will be able to see, hear and speak with you at all times using a two-way intercom. You will be given a device to notify the technologist if you’re uncomfortable or in distress. MRI scanners are air-conditioned and well-lit. Music may be played through the headphones to help pass the time.
In some cases, IV injection of contrast material may be given before the images are obtained. The IV needle may cause you some discomfort and you may experience some bruising. There is also a very small chance of skin irritation at the site of the IV tube insertion. Some patients may have a temporary metallic taste in their mouth after the contrast injection.
What are the limitations of MRI of the body?
High-quality images depend on your ability to remain perfectly still and follow breath-holding instructions while the images are being recorded. Motion during imaging may require you to return for additional scans.
A person who is very large may not fit into the MRI machine. The bore size (opening of the machine) and weight limits on the scanner determine this.
A very irregular heartbeat may affect the quality of images. This is because some techniques time the imaging based on the electrical activity of the heart.
Preparing for an MRI
An MRI machine is a high-powered magnet. Any ferrous (magnetic) substance can heat up or be fully attracted to the magnetic coil and removed from the body. Prior to your exam, you’ll be asked to fill out a screening form. This form is designed with your safety in mind. Any surgeries, piercings, or other contact with metal must be noted. Failure to disclose this information can be life threatening.