What Are the Differences between an MRI and fMRI?

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  • Written By: Mary McMahon
  • Edited By: Shereen Skola
  • Last Modified Date: 15 September 2019
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Magnetic Resonance Imaging (MRI) provides pictures of structures inside the body, while functional Magnetic Resonance Imaging (fMRI) evaluates metabolic processes. Both techniques can provide valuable insight into what is happening inside a patient’s body for medical testing, follow-up, and research. MRI can be used anywhere in the body, while fMRI studies concentrate on the brain, where imaging that can reveal very subtle changes in activity level is especially important. In some cases, patients may receive both MRI and fMRI scans.

In an MRI scan, the goal is to get an image of anatomical features in a given area of the body, like the abdomen. The equipment can be used to generate high-resolution images where various organs will appear as clearly distinct from each other, and abnormalities like tumors can be easy to spot. fMRI looks specifically at blood flow in the brain and is capable of detecting very small changes. This allows the test to identify when different areas of the brain become active, which can help a doctor or researcher see what a patient’s brain is doing. MRI and fMRI are typically ordered for very different reasons.


One key difference between MRI and fMRI is that MRI can generate static images that may be reviewed later for information about the inside of the patient’s body. In an fMRI study, the result is a real-time log of brain activity. It can be frozen at individual frames, such as a highlight of brain activity, or it may be viewed in video form later. Researchers might want to use fMRI to identify the areas of the brain involved in particular responses, for example, while a doctor might order the test to see why a patient can’t perform some cognitive tasks.

Before either MRI or fMRI, the patient needs to be screened to make sure the procedure will be safe. Patients can’t wear metal, and need to alert the technician to any medical or electrical implants in their bodies. They will also need to lie still in a potentially confined environment, unless a facility has an open MRI machine, which may require sedation to keep the patient calm. The equipment used in MRI and fMRI studies is loud, and some patients wear ear protection, which may include headphones with music to help them relax.

Patients may spend varying amounts of time in the equipment, depending on the purpose of MRI and fMRI. They should get an estimate before the procedure to help them plan. Some studies also require the use of contrast materials to increase the visibility of certain structures, in which case the patient receives an injection shortly before the imaging. Some contrast agents can cause allergic reactions, and patients should make sure the technician is aware of any allergy history.


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