MRI (Magnetic Resonance Imaging)

What is MRI (magnetic resonance imaging)?

MRI is a diagnostic procedure that uses a combination of a large magnet, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.

How does an MRI scan work?

The MRI machine is a large, cylindrical (tube-shaped) machine that creates a strong magnetic field around the patient. The magnetic field, along with a radiofrequency, alters the hydrogen atoms' natural alignment in the body. Computers are then used to form a two-dimensional (2D) image of a body structure or organ based on the activity of the hydrogen atoms. Cross-sectional views can be obtained to reveal further details. MRI does not use radiation, as do x-rays or computed tomography (CT scans). Some MRI machines look like narrow tunnels, while others are more open.

MRI may be used instead of computed tomography (CT) in situations where organs or soft tissue are being studied, because bones do not obscure the images of organs and soft tissues, as they do in CT. Because radiation is not used, there is no risk of exposure to radiation during an MRI procedure.

Due to the use of the strong magnet, MRI cannot be performed on patients with implanted pacemakers, intracranial aneurysm clips, cochlear implants, certain prosthetic devices, implanted drug infusion pumps, neurostimulators, bone-growth stimulators, certain intrauterine contraceptive devices, or any other type of iron-based metal implants. MRI is also contraindicated in the presence of internal metallic objects such as bullets or shrapnel, as well as surgical clips, pins, plates, screws, metal sutures, or wire mesh.

Another advance in MRI technology is the "open" MRI. Standard MRI units have a closed cylinder-shaped tunnel into which the patient is placed for the procedure. Open MRI units do not completely surround the patient, and some units may be open on all sides. Open MRI units are particularly useful for procedures involving:

children
Parents or other caregivers may stay with a child during the MRI procedure to provide comfort and security.
claustrophobia (Before the development of open MRI units, persons with severe claustrophobia often required a sedative medication prior to the procedure.)
very large or obese persons

Almost anyone can be accommodated in most open MRI units.

Reminders before the MRI Examination

Tell the radiologist if you are claustrophobic and think that you will be unable to lie still while inside the scanning machine; if you have a pacemaker inserted, or have had heart valves replaced; if you have metal plates, pins, metal implants, surgical staples, or aneurysm clips; if you have permanent eye liner; if you are pregnant; if you ever had a bullet wound; or if you have ever worked with metal (i.e., a metal grinder).

How is an MRI performed?

An MRI may be performed on an outpatient basis, or as part of inpatient care. Although each facility may have specific protocols in place, generally, an MRI procedure follows a stringent and involved process.

The MRI staff will be in another room where the scanner controls are located. However, the patient will be in constant sight of the staff through a window. The patient may be given headphones to wear to help block out the noises from the MRI scanner and hear any messages or instructions from the technologist.

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The content provided here is for informational purposes only, and was not designed to diagnose or treat a health problem or disease, or replace the professional medical advice you receive from your physician. Please consult your physician with any questions or concerns you may have regarding your condition.

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