Magnetic resonance imaging (MRI) uses a large magnet and radio waves to look at organs and structures inside your body. Health care professionals use MRI scans to diagnose a variety of conditions, from torn ligaments to tumors. MRIs are very useful for examining the brain and spinal cord.
During the scan on an open MR, you lie on a table that slides inside an open-environment magnet with two poles. Doing the scan can take from 15-25 minutes, and patient must stay still. The scan is painless. The MRI machine makes some noise during exam.
Before you get a scan, tell your doctor if you:
- Are pregnant
- Have pieces of metal in your body. You might have metal in your body if you have a shrapnel or bullet injury or if you are a welder.
- Have metal or electronic devices in your body, such as a cardiac pacemaker or a metal artificial joint.
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 is the most frequently used imaging test of the brain and spinal cord. It’s often performed to help in the diagnoses of:
- Disorders of the eye and inner ear
- Multiple sclerosis
- Spinal cord injuries
MRI can be used to view arteries and veins. Standard MRI can’t see fluid that is moving, such as blood in an artery, and this creates “flow voids” that appear as black holes on the image. Contrast dye (gadolinium) injected into the bloodstream allows, with the help of special software, to see the arteries and the veins. Contrast is also used to enhance viewing tumors and ateriovenous malformatios (AVMs).
An MRI may be used to check for tumors or other abnormalities of many organs in the body, including, but not limited to, the:
MRI may be used to help diagnose problems in joints, cases such as:
- 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
Lately, MRI is being used, in addition to mammography, to detect breast cancer. Particularly in women who have dense breast tissue or those who may be at high risk of the disease.
The presence of metal in the body of a patient may be a safety hazard or affect a portion of the MRI images. Before going through an MRI, tell the technologist if you have any metal or electronic devices in your body. Devices such as:
- Metallic joint prostheses
- Artificial heart valves
- An implantable heart defibrillator
- A pacemaker
- Metal clips
- Cochlear implants
- A bullet, shrapnel or any other type of metal fragment
You will also need to tell your doctor if you think you’re pregnant. The effects of magnetic fields on fetuses aren’t well understood. Your doctor will recommend choosing an alternative exam or postponing the MRI.
It’s also important to discuss any kidney or liver problems with your doctor and the technologist, because problems with these organs may limit the use of injected contrast agents during your scan.
Before an MRI exam, eat normally and continue to take your usual medications, unless otherwise instructed. You will be asked to change into a gown and to remove:
- Hearing aids
- Underwire bras
For some MRI exams, a contrast material called gadolinium will need to be injected into a vein in the arm.
While contrast material sometimes improves the MRI images, during pregnancy the exam will typically be performed without contrast material, and a radiologist (a doctor with expertise in medical imaging) will review the images. Contrast material will be used for the exam only if it is necessary to answer your doctor’s question.