How is the CT Head Scan Procedure Performed?

In a CT head scan, several x-ray beams pass through the skull and brain at different angles. Special sensors measure the amount of radiation absorbed by different tissues within the head. (This includes tissues that shouldn’t be there, such as lesions and tumours.)

In order to undergo a CT head scan, your general physician must write you a letter of referral stating why he or she believes a CT head scan is necessary in your situation. Once you have your referral, a CT head scan typically takes place either in a hospital or in an outpatient radiology center.

Prior to a CT head scan, some patients may need an injection of a contrast material, a material that differentiates soft tissue from other structures, prior to the exam. This material will “light up” the brain and other head tissue, making these structures more visible to the radiologist. This contrast material is injected through a small needle connected to an intravenous line inserted into a vein in the arm or hand.

During a CT head scan, the patient lies still on a table that is placed into the center of the CT scanner. The patient may lie on the stomach or on the back, depending on the type of examination. The CT scanner revolves around the patient and emits and records x-ray beams. The different areas of the head absorb different amounts of x-ray. A special computer program then forms graphical cross-sections based on these x-ray absorption differences. These cross-sections are called “tomograms.”

Once the patient enters the scanner, the technologist may turn on special lights to ensure the patient is positioned properly for the CT head scan. Some types of CT head scan (a scan of the sinuses, for example) require a special head holder made of soft straps to ensure the head and neck remain correctly aligned throughout the exam. An intercom within the scanner allows the patient and technologist to communicate throughout the procedure.

A CT head scan can take anywhere from 2 minutes to 45 minutes. The duration of the CT head scan depends on the number of images needed to get the information the doctor requires. At the conclusion of the CT head scan, the technologist will go over the images to make sure sufficient images have been made to fulfil the doctor’s request. More images may be necessary.