What Is a CT Scan?

The computed tomography (CT) scan is a medical imaging procedure that uses x-rays and digital computer technology to create detailed two- or three-dimensional images of the body. Unlike other forms of medical imaging, the CT scan can make an image of every type of body structure at once, including bone, blood vessels and soft tissue.

The CT scanning equipment consists of a large gantry (a supporting structure) with a circular hole. Inside the gantry is a rotating ring that carries the x-ray source and electronic x-ray detectors. An attached table slides the fully reclined person into the hole.

Multiple x-ray projections are taken in thin cross-sections along the person’s body (imagine a loaf of sliced bread). The detectors collect the x-ray information from each cross-section and send them to a special computer that combines them into an image.

The CT scan may also be referred to by its older name of computed axial tomography or ‘CAT’ scan.

When is a CT scan used?

Some of the common uses of the CT scan include:

• Assessment of a body part’s structure or shape
• Diagnosis of disease, particularly cancer
• Diagnosis of trauma or injury
• Diagnosis of vascular disease
• Aid to planning particular surgeries
• Aid to planning radiotherapy
• Visual aid to radiotherapy administration
• Visual aid to certain interventional procedures (going inside the body) such as biopsy or needle aspiration
• Measurement of bone strength
• Alternative to some types of exploratory or diagnostic surgery