What Are CT (CAT) Scans?

A computed tomography scan (CT scan), also called computed axial tomography scan (CAT scan), is a type of imaging test. It uses computers and a rotating X-ray machine to take cross-sectional pictures of the body. CT scans give doctors more detailed images than X-rays can provide. Unlike X-rays, they can show organs, soft tissues, and blood vessels in addition to bones.

CT scans are painless. A CT scan involves more exposure to radiation than a regular X-ray does, but the risk is small.

What Is a Head CT Scan?

A CT scan of the head uses a special X-ray machine to take pictures of the brain, skull, and sinuses, as well as blood vessels in the head.

A person getting a CT scan lies on a table. A pillow and sometimes a soft brace will hold their head and neck in place to prevent movement that would result in a blurry image. The donut-shaped machine circles the head, taking pictures to provide cross-sections of the brain from various angles. These pictures are sent to a computer that records the images. It also can put them together to form 3D images.

Why Are Head CT Scans Done?

Doctors may order a head CT scan to:

• check for conditions in the brain such as hydrocephalus, swelling, inflammation, bleeding, and signs of injury
• check for the presence, location, and size of abscesses, cysts, and tumors
• locate birth defects in the brain and skull
• look at malformed or injured blood vessels in the head
• find the cause of headaches, weakness, or a change in mental status

What if I Have Questions?

If you have questions about the head CT scan or what the test results mean, talk to your doctor.