Computed tomography, also called CT, of the brain is a noninvasive imaging method that combines X-rays with computer technology. X-ray beams from several angles are used to create a series of detailed cross-sectional images of the brain.
CT is an excellent method for viewing the structures of the brain quickly. It can provide detailed images of several types of tissue including bone, soft tissue, and blood vessels.
A cranial CT scan can help a doctor diagnose the following conditions: brain tumors and other abnormal brain growthsskull fracturesbrain damage after head injurybleeding in the brain after a strokediseases of the inner ear such as Meniere's diseaseruptured or leaking cerebral aneurysmshydrocephalus (literally, water in the brain )sinus diseaseold strokescongenital brain abnormalities brain atrophy or shrinkage often from a dementia such as Alzheimer's disease
Before the test, the doctor will ask the person if he or she: has any drug allergies or history of allergic reaction to medicinesis allergic to shellfish or to foods with added iodine such as table salthas ever had claustrophobia, which is a fear of enclosed or small spaces. If this is a problem, mild sedating medicine may be given.a woman will be asked if she might be pregnant. Often, a urine or serum pregnancy test will be done on females of childbearing age before the CT scan.
The person having a CT scan will first need to remove items that can interfere with the images, such as wigs, hairpins, clips, and removable dental hardware. The person lies on a flat platform with his or her head on a special pillow. This pillow provides comfort, which helps to limit movement during the scan. Next, the table slowly moves into the donut-shaped machine.
When the table is in the right position, the device delivers X-ray beams through the person's brain and skull from many angles. Often, a special substance called a contrast agent is used to enhance internal brain structures and improve the quality of the final images. Typically, the contrast agent is injected into a vein in the arm. Most CT tests take between 10 and 20 minutes. The scanning process is painless.
To make sure the final images are clear, the person must lie still during the whole exam.
The contrast agent may cause mild nausea in some people. Flushing, itching, and a metallic taste in the mouth are often described in patients who receive an injected contrast agent. Most of these feelings go away within a few minutes.
After the test, the person will be asked to wait until the pictures are looked at to see if any more are needed. The person will be observed for any delayed reactions to the contrast agent. To help rid the body of the contrast agent, he or she may be asked to drink extra fluids.
The CT technologist will explain how the test is done. A person who is prone to claustrophobia may require medication to calm him or her before the exam.
A doctor specially trained in analyzing CT images, called a radiologist, will examine the results of the test. He or she will forward a report of the findings to the person's healthcare professional, who will determine the significance of the findings in the context of the total clinical picture.
Pagana, Kathleen D. and Timothy J. Pagana, Mosby's Manual of Diagnstic and Laboratory Tests, St. Louis, 1998.
"Computed Tomography (CT) - Head," Radiological Society of North America (RSNA), 2000.