Magnetic resonance imaging, or MRI, has been around for more than four decades. The first MRI scan (in a more primitive form) was used in the 1970s. Today, there are many medical imaging tests, and it can seem confusing to know how they work and when they should be used.
One question many people have is, does MRI use radiation? In terms of potentially harmful ionizing radiation, no, it does not. An MRI scan is free of ionizing radiation as it works differently than other imaging tests that use it, such as X-rays, CT (computed tomography), and PET (positron emission tomography) scans.
That said, MRI does use radiation in the radiofrequency wavelengths. This type of radiation is found around us in normal daily life. It does not cause any damage to our bodies as it passes through, unlike ionizing radiation which may be harmful.
Here, we’ll look at how MRI scans work, the different types of MRI scans available, and the benefits and risk factors to consider when having an MRI scan.
You’ve likely heard of MRI and may have even had one in the past, but you might not know how it works. The technology behind MRI scans uses strong magnets to make a powerful magnetic field, which the person doesn’t feel. This makes the protons in the person’s body line up in the same direction as the magnetic field.
Protons are tiny particles found in the center of each atom — with atoms being the building blocks for every solid, liquid, and gas you can see or touch. The protons for the MRI scan are found in hydrogen atoms, which along with oxygen, make up water. The human body is comprised of around 60% water, which is why this technology works well.
The next stage of an MRI scan involves radio waves that are then passed through the patient causing the protons to try to move out of line with the magnetic field. When the radio waves are turned off, energy is released by the protons as they realign with the magnetic field. This energy is picked up by a powerful computer that turns it into MRI images.
Different types of tissue in the body will appear differently on the scan images, with detailed 3D images being produced, and any abnormalities shown.
An MRI scan is a non-invasive, painless type of scan. Magnets and radio waves are used in MRIs, so there is no ionizing radiation exposure to the patient.
MRI scans can be performed with or without contrast (a special dye, usually gadolinium). If contrast is needed, it’s injected into the person’s vein before or during the scan. In some scenarios, contrast dye is necessary to enhance the images. However, most soft tissues can be seen well without it.
The person lies face up on a flat cushioned bed and is moved into the MRI scanner. The scan takes between 15-90 minutes.
After a radiologist reviews the scans, they’ll send a report to the requesting healthcare practitioner who will discuss the results with the patient.
MRI scans are particularly useful for looking at soft tissues, such as muscle and fat. They can be used to look at areas across the whole body. These areas include:
While the examples presented are for diagnostic MRI scans (meaning they help to diagnose an existing condition), whole-body MRI scans are available for those who are asymptomatic (without symptoms), as a proactive approach to health. For instance, Ezra’s Full Body MRI can scan up to 13 organs and help detect possible cancer and other conditions before symptoms even arise.
There are different types of MRI scans. There is the traditional MRI scan, which can be performed with or without contrast dye. It can be performed on a particular area, such as the abdomen or brain, or as a full body MRI. Breast MRIs are carried out with a special breast coil to help visualize the breasts more clearly.
Specialized forms of MRI include functional MRI (fMRI), used in the brain to show which regions are using the most oxygen (and are therefore most active), such as when someone performs different cognitive (mental processing) tasks.
Other types of specialized MRI are an MRA (magnetic resonance angiography) or MRV (magnetic resonance venography), which visualize blood vessels — arteries or veins, respectively — and the blood flow through them.
There’s also an open MRI, which has flat magnets above and below the patient rather than in a circle all around them. This might be an option for patients with claustrophobia. However, open MRI images have reduced resolution due to weaker magnets. Moreover, they take longer and 360-degree imaging might not be possible.
The U.S. Food and Drug Administration (FDA) states there are no known health hazards from temporary exposure to the magnetic resonance environment. However, some patients will have risk factors to consider before having an MRI scan.
The American College of Obstetricians and Gynecologists recommends MRI scans for pregnant women only when necessary and on a case-by-case basis, in discussion with a healthcare practitioner. An MRI without contrast is much preferred. MRI scans and ultrasounds are considered the safer options for pregnant women needing imaging.
It’s rare but possible to have an allergy to contrast agents used in some MRI scans. If someone has a known allergy, it’s important to let the healthcare team know before the scan. Potential side effects from MRI contrast dye can include dizziness, trouble breathing, a rash, nausea, or vomiting.
The powerful magnets used for an MRI scan means the patient must go through a checklist before the scan to discuss any medical conditions and disclose if they have any metal on or inside their body. Any metal objects on the body, such as body piercings or an insulin pump, will need to be removed if possible.
If a patient has metal items that cannot be removed, they should discuss it with the technologist. MRI scans may not be performed on patients with certain types of metal inside or on their body.
While this is not an exhaustive list, the patient must let the scanning team know if they have any of the following:
If someone experiences claustrophobia, an MRI might be challenging. The scan involves lying on a bed that moves into the MRI machine, which is quite a small space. In some situations, a mild sedative can be requested ahead of time. An open MRI might be an option, if available. However, they have limitations, such as taking longer and lower image clarity.
Needing to Lie Still
An MRI takes at least 15 minutes and the person must lie still for much of this time. For some people this might be difficult. In these cases, the patient should discuss it with the radiology technologist performing the scan.
Noise
An MRI scan can be noisy. As such, earplugs or headphones playing music, an audiobook, or a podcast are usually provided. The patient will be able to talk to the technologist through a microphone and vice versa.
Children
If a child needs an MRI scan, special considerations can be made, such as giving them a virtual MRI tour beforehand or watching a movie. Some facilities offer child-friendly MRI scanners.
In terms of safety from ionizing radiation, MRI is safer than a CT scan, as MRIs don’t expose the person to any harmful radiation. CT scans use multiple X-rays, which expose the person to a level of ionizing radiation. Ionizing radiation means the molecules in the cells of someone's body can be changed, and this can increase the risk of cancer in the future.
The increase in risk after one CT scan is small, but increases if the person needs repeated CT scans. CT scans are useful in various situations, including emergencies such as acute bleeding or stroke, where the need for the scan would far outweigh any risks.
Both MRI and CT scans are used to help diagnose different conditions. The decision to use one of these imaging techniques over the other is usually based on the clinical need, which the person’s healthcare practitioner will guide them through. If someone requires multiple scans, and an MRI fits the clinical need, then this might be the best option for them.
MRIs use a strong magnetic field and radio waves to produce detailed images of organs and tissues inside the body. So does MRI use radiation? In terms of any potentially harmful ionizing radiation, no, it does not. The only radiation it uses is radio wave frequency—the same type that is found all around us every day. MRI scans are safe, and when no IV contrast is used, they are non-invasive. They are particularly good at visualizing soft tissues.
When used as a screening tool, a full-body MRI can help to pick up any abnormalities that would otherwise go unnoticed. And as we know, early detection is the best defense in the fight against cancer.
An Ezra Full Body MRI takes just one hour. You’ll receive your results within 5-7 business days via an Ezra Report that you may discuss with a healthcare professional via a telehealth visit. Take the first step in your proactive health journey and book your scan today.
