What to Expect During a Head CT
The technologist begins by positioning you on the CT examination table, usually lying flat on your back or on your stomach. Straps and pillows may be used to help you maintain the correct position and to hold still during the exam.
If contrast material is used, it will be injected through an I.V.
The table will move quickly through the scanner to determine the correct starting position for the scans. Then, the table will move slowly through the machine as the actual CT scanning is performed.
You may be asked to hold your breath during the scanning. Any motion can affect the quality of the images.
When the exam is complete, you will be asked to wait until the technologist verifies that the images are of high enough quality for accurate interpretation.
A CT scan of the head is usually completed within 10 minutes.
CT exams are generally painless, fast and easy. With helical CT, the amount of time that the patient needs to lie still is reduced.
Though the scanning itself causes no pain, there may be some discomfort from having to remain still for several minutes.
If an intravenous contrast material is used, you will feel a slight prick when the needle is inserted into your vein. You may have a warm, flushed sensation during the injection of the contrast materials and a metallic taste in your mouth that lasts for a few minutes. Some patients may experience a sensation like they have to urinate but this subsides quickly.
When you enter the CT scanner, special lights may be used to ensure that you are properly positioned. With modern CT scanners, you will hear only slight buzzing, clicking and whirring sounds as the CT scanner revolves around you during the imaging process.
You will be alone in the exam room during the CT scan. However, the technologist will be able to see, hear and speak with you at all times.
If the patient is a child, a parent may be allowed in the room but will be required to wear a lead apron to prevent radiation exposure.
Limitations of CT Scanning of the Head
A person who is very large may not fit into the opening of a conventional CT scanner or may be over the weight limit for the moving table.
Compared to MR imaging, the precise details of soft tissue (particularly the brain, including the disease processes) are less visible on CT scans. CT is not sensitive in detecting inflammation of the meninges—the membranes covering the brain.