What is an MRI and how does it work?

An MRI is a magnetic resonance imaging device used to create medical images in order to obtain detailed views inside the body. MRI machines use powerful magnets and software technology used by medical professionals to diagnose medical injuries or to asses how well a patient is responding to various treatments.

One of the benefits of using MRI is that unlike X-rays and CTs, MRI machines do not use radiation to generate images. An MRI is also able to provide highly detailed views of soft tissues such as joints, cartilage, ligaments, muscles and tendons, as well as surrounding structures inside the body.

When getting an MRI, patients typically lay down on a table that is inserted into a large circle opening of the machine that includes a powerful magnet inside.The magnet creates a magnetic field that interacts with the protons of the billions of hydrogen atoms inside our bodies. These interactions produce a signal that is detected by a receiver inside the MRI scanner. And then advanced software uses these signals to create detailed images.

Some common application for an MRI medical image include:

  • The brain, head and neck
  • Breasts
  • Spinal cord
  • The circulatory system
  • The heart
  • Other internal organs

Despite MRIs proving safe and effective in many circumstances, the strong magnets can interfere with certain devices such as pacemakers, metal joint replacements, and other implants. (You should consult your doctor or medical professional if you suspect that there is any metal inside your body prior to getting an MRI.)

There are many forms of MRI scans. Two of the most common are diffusion MRI and functional MRI (fMRI).

Diffusion MRIs are often used when looking for tumors and strokes because these can cause variations in how the water molecules inside the body “diffuse” through various body tissues.

MRI can also be used to visualize various “functions” in the body such as blood flow through the brain, heart or other parts of the body. Functional MRI, or fMRI, can measure these changes in blood flow to provide detailed images.

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What to expect during an MRI

People receiving an MRI are asked to lay down on a table that moves into the opening of the machine. Once your scan begins, it is common to hear many different sounds and to have hearing protection for your comfort. 

In certain cases, participants are given an intravenous liquid dye in order to provide a contrast in the images required.

For patients who report common feelings of claustrophobia or anxiety, they may be given a mild sedative to calm them during the duration of the scan. And some medical facilities offer an “open MRI” that does not fully surround the participant on all sides as an alternative.

The scans may take anywhere from 20-45 minutes. And afterwards, a radiologist reviews the images and provides a report for your doctor.