Magnetic resonance imaging or MRI was developed from nuclear magnetic resonance (NMR) in the 1970’s by Dr. Raymond Damadian. NMR had industrial uses for evaluating structural components. Dr. Damadian used NMR to study potassium ions in the human body and proposed that tumors could be visualized with the images he was able to generate.
In simple terms, an MRI is a giant electromagnet is which the patient is placed. The entire room is shielded in copper to block out external FM radio waves. When the magnet is turned on, all the water molecules in the body line up with the magnetic field. The water molecules also absorb FM radio waves generated by the MRI.
When the magnet is turned off the water molecules resume their normal orientation. This has two measurable effects: First, the molecules emit the same FM radio waves they absorbed. Second, the molecules “wobble” slightly as they reorient, creating their own magnetic field.
This data is stored in the computer showing where all the water molecules are located throughout the human body. The computer then can generate holographic images depicting the location of the water.
There are also two sets of images. The T1 views are created from the FM signal from the water molecules. The T2 images are built from the data from the magnetic “wobble”. Comparing the T1 to T2 images yields additional insight as the images highlight tissues quite differently.
Bone, being virtually devoid of water, is imaged as an absence of any signal. So MRI is quite limited in its’ ability to “see” bone. However, tumors, infection, and even fracture involve the inclusion of water so these pathologies actually light up very well on MRI.
