(c) Anthony K. Grafton 2003

The Science of MRI

Chances are you know someone who has had a medical scan known as an MRI. This scan, known by its full name as magnetic resonance imaging, provides doctors with a wealth of information in a quick, painless way.

Magnetic resonance imagery works because of the physics of atoms. All atoms have a small, heavy, central area known as a nucleus. Some atomic nuclei are similar to tiny bar magnets. Like any magnet, these nuclei interact with other magnetic fields that might be around them.

When someone gets an MRI, he or she is placed in a machine that creates a very strong magnetic field. In a perfectly harmless way, the nuclei of many of the atoms that make up the patient’s body react to this magnetic field by lining up with it. Next, radio waves, which are also harmless, are sent through the patient, causing some of the atomic nuclei to flip over. When these flipped nuclei then realign with the magnetic field, they in turn emit more radio signals. Monitoring these emitted radio signals with sophisticated detectors and processing them through computers allows doctors to reconstruct a detailed image of the inside of the patient’s body.

Chemists regularly use this same technique in the lab to study the structures of molecules and proteins, but they call it NMR (nuclear magnetic resonance). Many other advances in basic science have resulted in profound benefits to mankind. How many medical techniques commonly used today would not exist without the last century of scientific discovery?