Magnetic resonance imaging (MRI) is a technique that uses a magnetic field and radio waves to create detailed images of the organs and tissues within your body.
Most MRI machines are large, tube-shaped magnets. When you lie inside an MRI machine, the magnetic field temporarily realigns hydrogen atoms in your body. Radio waves cause these aligned atoms to produce very faint signals, which are used to create cross-sectional MRI images — like slices in a loaf of bread.
The MRI machine can also be used to produce 3-D images that may be viewed from many different angles.
Why Do I Need an MRI?
MRI is a noninvasive way for your doctor to examine your organs, tissues and skeletal system. It produces high-resolution images that help diagnose a variety of problems.
MRI of the brain and spinal cord
MRI is the most frequently used imaging test of the brain and spinal cord. It’s often performed to help diagnose:
- Disorders of the eye and inner ear
- Multiple sclerosis
- Spinal cord injuries
- Functional MRI of the brain (fMRI) can be used to identify important language and movement control areas in the brain in people who are being considered for brain surgery.
MRI of the heart and blood vessels
An MRI that focuses on the heart or blood vessels can assess:
- The size and function of the heart’s chambers
- Thickness and movement of the walls of the heart
- The extent of damage caused by heart attack or heart disease
- Structural problems in the aorta, such as aneurysms or dissections
- Inflammation or blockages in the blood vessels
- MRI of other internal organs
An MRI may be used to check for tumors or other abnormalities of many organs in the body, including the:
- MRI of bones and joints
MRI may be used to help evaluate:
- Joint disorders, such as arthritis
- Joint abnormalities caused by traumatic or repetitive injuries
- Disk abnormalities in the spine
- Bone infections
- Tumors of the bones and soft tissues
- MRI of the breasts
MRI may be used in addition to mammography to detect breast cancer, particularly in women who have dense breast tissue or who may be at high risk of the disease.
What to Expect
Patients do not feel any pain while undergoing an MRI and no special diet or preparation is required before this exam. They are asked to remove anything metal, which includes jewelry and even bras, which typically have metal clasps, and may be asked to change into a hospital gown if their clothing has metal zippers or buttons. Otherwise, wearing clothes should be fine.
The examination table is fairly narrow and slides out from the tubular machine. It is very important that patients lie completely still during the procedure in order to obtain the clearest image. Patients are easily able to communicate through an intercom.
MRI tests could take as little as 15 minutes or as long as two hours, depending on the type of study. Some examinations require an injection of a contrast agent into a vein to better view certain areas of the body. Our radiologists help patients feel as comfortable as possible during their exam. We offer earplugs to all patients to minimize the volume of sound from the testing equipment. Immediately following the scan, patients may resume normal activities.
Because MRI uses magnets to create images, patients with pacemakers and some other implanted devices cannot undergo MRI. If you are going to have an MRI and you have an implanted device inside your body, please let the technologist or radiologist know prior to your study.