MRI

Magnetic Resonance Imaging

WHAT IS MRI AND HOW DOES IT WORK?

Magnetic resonance imaging, or MRI, is a way of obtaining very detailed images of organs and tissues throughout the body without the need for x-rays or “ionizing” radiation. Instead, MRI uses a powerful magnetic field, radio waves, rapidly changing magnetic fields, and a computer to create images that show whether or not there is an injury, disease process, or abnormal condition present.

For the MRI procedure, the patient is placed inside of the MR scanner—typically a large doughnut-shaped device that is open on both ends. The powerful magnetic field aligns atomic particles called protons that are present in most of the body’s tissues. The applied radio waves then cause these protons to produce signals that are picked up by a receiver within the MR scanner. The signals are specially characterized using the rapidly changing magnetic field, and, with the help of computer processing, images of tissues are created as “slices” that can be viewed in any orientation.

An MRI examination causes no pain, and the magnetic fields produce no known tissue damage of any kind. The MR scanner may make loud tapping, knocking or other noises at times during the procedure. However, using earplugs prevents problems that may be associated with this noise. You will be able to communicate with the MRI technologist or radiologist at any time using an intercom system or by other means.

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WHAT IS MRI USED FOR?

MRI is the preferred procedure for diagnosing a large number of potential problems or abnormal conditions in many different parts of the body. In general, MRI creates pictures that can show differences between healthy and unhealthy tissues. Physicians use MRI to examine the brain, spine, joints (e.g., knee, shoulder, hip, wrist, and ankle), abdomen, pelvic region, breast, blood vessels, heart and other body parts.

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HOW SHOULD I PREPARE FOR MY MRI EXAM?

You will typically receive a gown to wear during your MRI examination. Before entering the MR system room, you and any accompanying friend or relative will be asked questions (i.e., using a screening form) regarding the presence of implants and will be instructed to remove all metallic objects from pockets and hair. Additionally, the accompanying individual will need to fill out a screening form to ensure that he or she may safely enter the MR system room. If you have questions or concerns, please discuss them with the MRI technologist or radiologist prior to the MRI examination.

Before the exam you will be asked to fill out a screening form asking about anything that might create a health risk or interfere with imaging. Items that may create a health hazard or other problem during an MRI exam include:

• Cardiac pacemaker or implantable defibrillator

• Catheter that has metallic components that may pose a risk of a burn injury

• A ferromagnetic metallic vascular clip placed to prevent bleeding from an intracranial aneurysm

• An implanted or external medication pump (such as that used to deliver insulin or a pain-relieving drug)

• A cochlear (inner ear) implant

• A neurostimulation system

• A catheter that has metallic components that may pose a risk of a burn injury

Important note: Some items, including certain cardiac pacemakers, neurostimulation systems and medication pumps are acceptable for MRI. However, the MRI technologist and radiologist must know the exact type that you have in order to follow special procedures to ensure your safety.

Items that need to be removed by patients and individuals before entering the MR system room include:

• Purse, wallet, money clip, credit cards, cards with magnetic strips

• Electronic devices such as beepers or cell phones

• Hearing aids

• Metal jewelry, watches

• Pens, paper clips, keys, coins

• Hair barrettes, hairpins

• Any article of clothing that has a metal zipper, buttons, snaps, hooks, underwire, or metallic threads

• Shoes, belt buckles, safety pins

Objects that may interfere with image quality if close to the area being scanned include:

• Metallic spinal rod

• Plates, pins, screws, or metal mesh used to repair a bone or joint

• Joint replacement or prosthesis

• Metallic jewelry including those used for body piercing

• Some tattoos or tattooed eyeliner (these alter MR images, and there is a chance of skin irritation or swelling; black and blue pigments are the most troublesome)

• Makeup, nail polish or other cosmetic that contains metal

• Bullet, shrapnel, or other type of metallic fragment

• Metallic foreign body within or near the eye (such an object generally can be seen on an x-ray; metal workers are most likely to have this problem)

• Dental fillings (while usually unaffected by the magnetic field, these may distort images of the facial area or brain; the same is true for orthodontic braces and retainers)