CT scan or CAT scan, short for computed tomography, is a special kind of imaging that uses multiple x-rays at different angles and in layers to create an extremely detailed cross-section view of the inside of the body. CT scans are fast and can show unusually accurate images of soft tissue. They are often used to detect tumors, look for clots in blood vessels, and pinpoint internal damage after a trauma.
When receiving a CT scan, you lie on a table which moves through a circular opening. Inside the machine, an x-ray transmitter and receptors spin around your body, taking multiple pictures in thin 'slices' a few millimeters thick. A computer then combines all of the information into a series of images showing the inside of your body.
Because a CT scan uses radiation, it is not usually recommended for pregnant women. However the level of radiation is actually quite low -- less than you would receive while taking a long airplane flight. Unlike with an MRI, you can have a CT scan even if you have metal devices implanted within your body. You do have to lay still in order to get an accurate scan, and at times you may even be asked to briefly hold your breath. Some CT machines can make quite a bit of noise during the procedure, usually clicking or buzzing. However most CT scans are fast, so even noise or holding still is very tolerable.