Magnetic Resonance Imaging (MRI): Indications and Contraindications

Magnetic resonance imaging (MRI) is a painless test that produces very clear images of the organs and structures within the body. MRI uses a large magnet, radio waves and a computer to produce these detailed images. It does not use X-rays (radiation).

Magnetic Resonance Imaging (MRI)

What is it like to have a magnetic resonance imaging (MRI) scan?

Many people are nervous about a magnetic resonance imaging (MRI) test because they fear being enclosed in a tight space. It’s true that the older machines were narrow with the tight head-to-ceiling space. However, newer machines have greatly improved patients’ comfort. The newer machines are “open bore,” meaning they are open at both ends. The newer MRI machines also have wider openings, shorter total length, better interior lightening, more head-to-ceiling space, more arm/body room, and are fully ventilated (a fan will blow a gentle stream of air on you). In some cases, if only a lower body scan (legs and lower) is needed, a patient’s head and torso can remain outside the machine.

If you are nervous about the MRI test or fear closed spaces, talk to your doctor. If needed, your doctor will discuss options for medicine or even anesthesia if necessary.

What your healthcare team needs to know about you before your magnetic resonance imaging (MRI) test

The magnetic resonance imaging (MRI) scanner uses strong magnets and radio wave signals that can cause heating or possible movement of some metal objects in your body. This could result in a health and safety issue. It could also cause some implanted electronic medical devices to malfunction. If you have metal-containing objects or implanted medical devices in your body, we need to know about them before your exam. Certain implanted objects may require additional scheduling arrangements and special instructions. Other items do not require special instructions but may require an X-ray to check on the exact location of the object before your exam. Please tell your doctor and MRI technologist if you have any of the following:

• Heart pacemaker/defibrillator.
• Electronic/implanted stimulators or devices, including deep brain stimulator, vagus nerve stimulator, bladder stimulator, spine stimulator, neurostimulators; implanted electrodes or wires.
• Cochlear implant or other ear implants.
• Implanted drug pumps (insulin, narcotic/pain medications, drugs to treat spasticity).
• Programmable shunt.
• Aneurysm clips and coils.
• Stents (not located in heart).
• Filters (for example, blood clot filters).
• Metal fragment in your body or eye (eg, BBs, bullets, shrapnel, metal pieces or shavings) .

The following items will not be able to be worn during your MRI. Please coordinate your MRI appointment with the day you need to change your patch/device

• Continuous glucose monitors.
• Medication patches .
• Insulin pump.

In addition, tell the doctor if you:

• Are pregnant.
• Are not able to lie on your back for 30 to 60 minutes.
• Have claustrophobia (fear of closed or narrow spaces).

How long is the magnetic resonance imaging (MRI) exam?

Allow 2 hours for your MRI exam. In most cases, the procedure takes 40 to 80 minutes.

What should I expect before, during and after the magnetic resonance imaging (MRI) exam?

Before the exam

• If you have been given an implant card to carry in your wallet, be sure to bring it with you to your MRI appointment.
• Personal items such as your watch, wallet -- including any credit cards with magnetic strips (they will be erased by the magnet) -- and jewelry/body piercing jewelry should be left at home if possible, or removed prior to the MRI scan. Secured lockers are available to store personal possessions. Other metal objects that need to be left at home or stored in the locker include dentures/partial plants, eyeglasses, hearing aids, hair pins/barrettes, keys, cell phones and beepers.
• You will be required to change into a hospital gown for the MRI scan.
• Certain MRI exams require an injection of a contrast material called gadolinium. The contrast adds additional information to the pictures on some diagnoses. If your doctor ordered an MRI with contrast, the contrast material will be injected into an IV line that has been inserted into your hand or arm.

During the exam

• You will lie face up for most exams on the MRI scanning bed. The MRI scanning bed will slide into the MRI machine.
• As the MRI scan begins, you will hear the equipment making a variety of loud knocking and clicking sounds. Each series of sounds may last for several minutes. You will be given ear plugs or headphones to wear to protect your hearing before the procedure begins.
• You are required to lay perfectly still during the exam.
• The MRI technologist can see you and is able to talk with you at all times. An intercom system allows two-way communication while you are inside the scanner. You will also be given a call button that you can push to let the technologist know if you are having any problems or concerns.

After the exam

• Generally, you can resume your usual activities and normal diet immediately. If you received anesthesia, please follow the home-going instructions given to you by the radiologist (including having a responsible person with you to drive you home).
• The results of your MRI should be available to your physician within 24 hours after your test, Monday through Friday.
• Your physician will discuss the test results with you.

Please talk to your doctor if you have any concerns or questions about your upcoming MRI exam. Also, if you have questions about any implant you may have in your body, be sure to ask your doctor or MRI technologist.