What Do Implants, Metal and Noise Have To Do With an MRI Scan?
Scheduled for an MRI? Here's what you need and want to know.
What is an MRI (magnetic resonance imaging) scan?
An MRI is an imaging exam that uses strong magnets and radio waves to generate detailed images of organs and other structures inside the body. It’s used to diagnose a variety of conditions from torn ligaments to heart disease to possible tumors. Some MRI exams require a contrast agent — a dye — which is injected through an intravenous (IV) line to illuminate problem areas.
An MRI provides information that’s different from a CT (computed tomography) or a PET (positron emission tomography) scan. And unlike a CT or PET scan, an MRI does not require radiation.
Remove all metal before this test and tell the technologist if you have any medical devices, such as an implant or joint replacement, that might contain metal. The metal may interact with the magnets in the MRI scanner and cause problems.
Can I have an MRI if I have an implant (breast, knee or hip)?
Not all metallic devices will prevent you from having a scan. However, the technologist needs to consider each device prior to allowing you to enter the MRI exam room. That’s because MRI scanners use powerful magnetic fields to generate internal images. Metal or metallic devices may create shadows that obscure diagnostic information. In some instances, magnetic fields may cause the implanted metal device to heat up, move or even malfunction. For this reason, patients are screened for magnetic or other devices through a series of questions prior to entering the MRI suite.
Alert your doctor if you have a cardiac pacemaker or possibly a cerebral aneurysm clip placed prior to 1995. Other types of implants such as breast implants, hip prostheses, and knee prostheses are generally safe in the MRI scanner. Braces on the teeth also are considered safe although the metal in the braces may create shadows which obscure portions of the imaged area.
Why is an MRI exam so noisy?
Blame the noise on the magnets inside the MRI scanner and the electric current running through its coiled wires. The resulting electromagnetic radio frequencies are so powerful that they cause the wire to vibrate, which results in the banging noise you hear.
These rhythmic noises are part of the device’s ability to make pictures of the body and are not a malfunction. Many patients opt to listen to music as the test is being performed.