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What is an MRI Scan? - Definition, Uses & Side Effects

Instructor: Jenna Liphart

Jenna teaches undergraduate nursing courses and has a master's degree in nursing education.

MRI scanners are imaging machines used in the medical field. MRI machines are safe and used frequently with a wide variety of patients. Learn about what MRI scanners are, their uses, and potential side effects.

What Is an MRI Scanner?

Have you ever seen a medical drama television show where the physicians look at really detailed pictures of the brain? Did you wonder how they got that picture? It was most likely an MRI scanner that took it! Medical imaging allows physicians to see the inside of the body without having to perform surgery and risk complications. This ability has changed the course of medicine and health care for the better.

MRI (magnetic resonance imaging) scanners are machines used in the medical field to take pictures of body structures and functions. Unlike most other imaging machines, MRI scanners do not use radiation (x-rays); they use large, powerful magnets. During an MRI scan, the patient lays down inside a large tube while the magnets inside the tube create radio-frequency waves that produce very detailed pictures of the inside of the body.

Each cell in the body is made of hydrogen and oxygen molecules, and in the middle of each hydrogen atom, a very small proton particle exists. These proton particles are pulled by the magnets in the MRI scanner and line up in a way that can be seen when radio-frequency waves are produced. The detailed images are then seen on a screen by the MRI technologist running the machine and the radiologist, who is the physician who specializes in interpreting these images.

MRI scanners are useful for internal examination of any part of the body. They are particularly useful for physicians to examine tumors, joints, the brain, and the spinal cord.

How Is an MRI Scan Performed?

MRI scans are very safe procedures with minimal risk. Since the MRI machine uses powerful magnets, no metal is allowed into the room where the machine is located. You will be screened by an MRI technologist before entering to ensure you are free of metal. Due to this, those with pacemakers, orthopedic hardware (pins or joint replacements), and orthodontic hardware (braces) may not be eligible for an MRI scan.

While you are having an MRI scan, you will lie down on a bed that moves in and out of the magnetic tube. If you suffer from claustrophobia, the scan may be uncomfortable for you, but let the technologist know so they can help you manage it.

MRI machines can make loud 'knocking' sounds and sometimes vibrate- this is normal. The MRI technician will either give you ear plugs to block out the noise or headphones so that you can listen to music to cover the noise and also still hear them speak to you.

MRI scans can last anywhere from 20-90 minutes. It is important that you stay as still as possible while in the machine because movement causes the pictures to be blurry and require them to be retaken.

Are There Any Side Effects?

There are minimal side effects for those who have been screened by the technologist and deemed free of metal. There has been no evidence found to suggest that there are harmful side effects from MRI scanners.

However, if you suffer from claustrophobia you may feel anxious. Some patients have reported a slight headache or backache during the scan due to lying down for an extended period of time, but these symptoms subside once the scan is over.

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