MRI scans use large, powerful magnets and a specialized computer to produce high-resolution cross-sectional images of the bones and soft tissues. Unlike X-rays and computerized tomography (CT) scans, MRI works without radiation.
MRI scans are not painful but they can be very noisy, with a lot of tapping or thumping noises, so earplugs or headphones may be used to muffle the sound.
What Is an MRI Used For?
MRI (magnetic resonance imaging) scans are used to image soft tissues or non-bony parts of the body such as the:
- Bones and joints
- Heart and blood vessels
- Internal organs
- Spinal cord and nerves
How Do Doctors Perform an MRI?
Prior to an MRI (magnetic resonance imaging) scan, patients need to remove metals and other objects that might affect the magnetic imaging, such as:
- Hearing aids
- Underwire bras
- Cosmetics that contain metal particles
- Hair accessories
During an MRI scan, a patient usually lies on a table that slides into a tube-shaped MRI scanner, which is the bore of the magnet, for imaging.
- An electric current is passed through coiled wires to create a magnetic field in a patient’s body in the area of the body to be imaged.
- Radio waves cause the tissues to vibrate and so that digital images of the scanned area of the body are then created.
- A computer records the rate at which the body part emits the vibrations, and then translates the data into a two-dimensional picture.
- During the exam, the patient can communicate with a technologist who is in another room.
- In some cases, intravenous (IV) gadolinium-based contrast agents (GBCAs) are used to enhance the contrast and detail of the images.
How Long Does an MRI Take?
- MRI scans usually last between 20 to 90 minutes, depending on the part of the body being imaged.
What Are Risks and Complications of an MRI?
Complications and side effects of MRI (magnetic resonance imaging) are uncommon, but there are some considerations:
- Implanted devices and foreign bodies
- Those who have pacemakers, insulin pumps, cochlear implants, implantable cardioverter-defibrillators, vagus nerve stimulators, loop recorders, deep brain stimulators, and capsules from capsule endoscopy should not get an MRI
- Claustrophobic patients
- These patients may require sedation or may need to have an open MRI
- MRI scans should generally be avoided, especially in the first trimester
- Gadolinium contrast agent
- Patients on dialysis may have a severe reaction to use of these agents
- Agitated patients
- Young children or anyone unable to stay still may need sedation
- Unstable patients
- May not be able to tolerate an MRI
- Obese or large patients
- May be unable to fit into the cylinder of the MRI system
- May be able to be accommodated in an open MRI
- MRI machines can be very noisy and ear protection may be needed
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