What Is MRI? – May 2019

by Michael Wang, MD

MRI stands for Magnetic Resonance Imaging and is the best imaging technique for soft tissues.

MRI uses a strong magnetic field and radiofrequency waves to create images of the body. There is no harmful radiation or effects in clinical MRI.

How strong is an MRI magnet? A 1.5 Tesla MRI magnet is 30,000 times stronger than the Earth’s magnetic field.

In the photos below metal equipment was sucked into the bore of the MRI and can only be removed by completely powering down the MRI which is an expensive and time-consuming process. This is why most metal is not allowed in an MRI room.

MR imaging is based upon the presence of Hydrogen atoms in the body.

Almost everything in our bodies contains Hydrogen atoms: Organs, Blood, Fat, Bone (marrow), Cartilage, Nerves, Muscles

The following structures in our bodies have relatively LITTLE Hydrogen: Lungs (air), Ligaments, Tendons

The magnetic field aligns the Hydrogen atoms in your body to the strong magnetic field.

Radio waves are transmitted into your body which shift the Hydrogen atoms slightly and sensitive detectors detect the shift.

Because the Hydrogen characteristics of each tissue is so different MRI provides the best contrast resolution which is needed to evaluate soft tissue including:

Ligaments, tendons, muscles, cartilage, labrum, discs, nerves, brain, liver, kidneys, pancreas, and reproductive organs.

A properly performed MRI takes 20-25 minutes for each body part. 

Being still during the imaging procedure is extremely important to obtaining clear pictures.