Asked by Jeri, Tennessee
I learned I had breast cancer early this year. I also have heart problems that led to placement of two stents. Is it possible to get MRI's of my breasts or other parts of my body with stents in place?
Dr. Otis Brawley
Chief Medical Officer,
American Cancer Society
This is an excellent question. Magnetic resonance imaging, or MRI, is commonly used and growing in preference because it does not use radiation.
Instead of using radiation to make an image as X-ray or CT scanning does, magnetic resonance imaging creates a very strong magnetic field. The magnetic field is turned on and off. This makes water molecules in body tissues give off a signal. The signal is picked up by an "antenna-like" sensor and an image is created.
Certain metals are ferromagnetic, meaning they are subject to magnetic fields. The concern is a magnetic field can cause a ferromagnetic object to move and in some cases even spin. Imagine the harm that could occur if an object with ferromagnetic material inside a patient were to start moving.
Fortunately, implantable objects are common and most are designed with the MRI in mind. In 2007, the American Heart Association published guidance on the safety of magnetic resonance imaging in patients with cardiovascular devices.
This statement covers coronary artery stents, artificial valves, pacemakers and even metal wire suture used in heart surgery. It applies to any type of MRI procedure, be it imaging the breast, head, torso or an extremity.
First, you should consult the doctor who placed the object if you were not provided information at the time of placement. Many doctors give their patients written information on the implanted device and how to live with it safely. This is usually done at discharge right after the device is implanted.
There is a lot going on at that time and it's not unusual for patients to not realize its importance. If a device is nonferromagnetic, MR imaging can be performed without concern. Some devices are weakly ferromagnetic. Patients with these devices, should try to avoid MR imaging immediately after implantation. Tissue healing takes several weeks and aids in device anchoring. It is prudent to delay nonemergency imaging until approximately six weeks after implantation.
Exceptions are sometimes made for emergency or crucial tests. In these circumstances, the patient and health care provider must weigh the risks and benefits of scanning.
Most coronary artery stents have been tested and are nonferromagnetic. Patients who got a stent after 2007 still should consult with the physician who placed the stent, but virtually all made after 2007 are safe for MR imaging.
It is still generally recommended that the magnet strength be 3 Tesla or less. The majority of prosthetic heart valves are labeled "MR safe." A few have been labeled "MR conditional." These, too, are generally safe. Patients with heart valves should consult their physician before MR imaging, but it should be safe to do the procedure in a machine whose magnet strength is 3 Tesla or less any time.
Permanent pacemakers and implantable cardioverter-defibrillators have ferromagnetic elements within them. MR imaging can cause the device to move as well as interfere with its electronic functioning. Even though some patients with these devices have been scanned safely, having a pacemaker or implantable defibrillator generally means you should not have an MR examination.
If scanning must be performed, it should be done only at highly experienced centers with expertise in MR imaging and cardiac electrophysiology (operation of pacemakers and defibrillators).
Most patients who have open heart surgery for coronary artery bypass or valve replacement have sternal wires. These are metal wires used to hold the front of the ribcage (breastbone) together. They are generally considered safe for MR scanning. Sternal wires, pacemakers, and implantable cardioverter-defibrillators will interfere with the quality of the image produced.
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