A Moment of Science

Scans, Scans, and More Scans

MRI, CT, PET... What are all these scans used for and how are they different?

a CT scan of a persons skull in front of a light

Photo: Akira Ohgaki

A CT scan is essentially a three dimensional x-ray. Detectors mounted inside a spinning disk rotate to capture slice-like images at hundreds of different angles.

Go to the hospital to have a doctor check out an internal problem, and you’re liable to hear about MRI scans, CT scans, and PET scans. All of these scans take detailed pictures of your body’s insides.

What sets MRI, CT, and PET scans apart is how they work. MRI stands for magnetic resonance imaging. An MRI scanner uses several large, very cold magnets to create a powerful magnetic field that reads the spin and interaction of your body’s electrons and protons. The resulting images can be very specific, pinpointing tiny sections of any part of the body.

A CT scan, which stands for computerized tomography, is also good at revealing internal tumors and lesions. A CT scan is essentially a three dimensional x-ray. Detectors mounted inside a spinning disk rotate to capture slice-like images at hundreds of different angles. This allows doctors to get a detailed, overall look at a given region of the body.

A PET scan is a bit different. PET is short for positron emission tomography. To do a PET scan, a doctor injects you with a radioactive isotope that decays and emits positrons, which are positively charged antimatter relatives of electrons. When positrons and electrons come together they annihilate each other and give off energy in the form of gamma rays. PET scan images are valuable because they not only show tumors but can reveal the metabolic state of a tumor, such as whether it is cancerous or benign.

Together, MRI, CT and PET scans give doctors an unprecedented glimpse into the inner workings of the human body.

Stay Connected

What is RSS? RSS makes it possible to subscribe to a website's updates instead of visiting it by delivering new posts to your RSS reader automatically. Choose to receive some or all of the updates from A Moment of Science:

Support for Indiana Public Media Comes From

About A Moment of Science

Search A Moment of Science