What's the difference between a PET scan and a CT scan?

A PET scan and a CT scan show different kinds of information, even though they are often done together. A CT scan uses special x-ray equipment to make detailed pictures of the structures inside your body. A PET scan is a type of nuclear scan that makes detailed 3-D pictures of areas where glucose, or sugar, is taken up — and because cancer cells often take up more glucose than healthy cells, this can help find cancer that might not be as clear on structural images alone.

Before a PET scan, you receive an injection of a tracer called radioactive glucose, and then you lie still on a table that moves through the scanner while it detects where that tracer has gathered.

PET is often combined with CT, done at the same time using one machine. This combination, sometimes written as PET/CT, gives your care team more detailed pictures than either scan alone, pairing the structural detail of CT with the activity information from PET.