How should I prepare for the CAT scan?
You should wear comfortable, loose-fitting clothing to your exam. You may be given a gown to wear during the procedure.
Metal objects including jewelry, eyeglasses, dentures and hairpins may affect the CT images and should be left at home or removed prior to your exam. You may also be asked to remove hearing aids and removable dental work.
You may be asked not to eat or drink anything for several hours beforehand, especially if a contrast material will be used in your exam. You should inform your physician of any medications you are taking and if you have any allergies, especially to contrast materials.
Also inform your doctor of any recent illnesses or other medical conditions, and if you have a history of heart disease, asthma, diabetes, kidney disease or thyroid problems. Any of these conditions may increase the risk of an unusual adverse effect.
Women should always inform their physician or technologist if there is any possibility that they are pregnant. See the safety page for more information about pregnancy and x-rays.
If your infant or young child is having a spinal CT, there are measures that can be taken to ensure that the test will not be a cause of anxiety for either the child or parent.
CT scanning—sometimes called CAT scanning—is a noninvasive, painless medical test that helps physicians diagnose and treat medical conditions.
CT imaging uses special computerized x-ray equipment to produce multiple images that provide a cross-sectional view of the inside of the body in the area being studied.
CT scans of internal organs, bone, soft tissue and blood vessels provide greater clarity than the conventional x-ray exams.
Using CT, the bony structure of the spinal vertebrae is clearly and accurately shown as are the intervertebral disks and, to some degree, the spinal cord.
What are some common uses of the procedure?
Perhaps the most frequent use of the spinal CT is to detect, or rule out, spinal column damage in patients who have been injured.
CT scanning of the spine is also performed to:
- Evaluate the spine before and after surgery.
- Detect various types of tumors in the vertebral column, including those that have spread there from another area of the body. Some tumors that arise elsewhere are first identified by finding deposits of malignant cells (metastases) in the vertebrae, prostate cancer is an example.
- Help diagnose spinal pain. One of the most common causes of spinal pain that may be diagnosed by CT is a herniated intervertebral disk, sometime with CT myelography
- Accurately measure bone density in the spine and predict whether vertebral fractures are likely to occur in patients who are at risk of osteoporosis.
- Guide diagnostic procedures such as a biopsy of a suspicious area to detect cancer or the removal of fluid from a localized infection (abscess).
- In patients with narrowing of the spinal canal, vertebral fracture, infection or degenerative disease such as arthritis, a CT of the spine may provide important information when performed alone or in addition to Magnetic Resonance Imaging (MRI).
What are some common uses of the procedure?
CT scanning of the head is typically used to detect:
- Bleeding, brain damage and skull fractures in patients with head injuries
- Bleeding caused by a ruptured or leaking aneurysm in a patient with a sudden severe headache
- A blood clot or bleeding within the brain shortly after a patient exhibits symptoms of a stroke
- A stroke, especially with a new technique called perfusion CT
- Brain tumors
- Enlarged brain cavities (ventricles) in patients with hydrocephalus
- Diseases or malformations of the skull
CT scanning is also performed to:
- Evaluate the extent of bone and soft tissue damage in patients with facial trauma and planning surgical reconstruction
- Diagnose diseases of the temporal bone on the side of the skull, which may be causing hearing problems
- Determine whether inflammation or other changes are present in the paranasal sinuses
- Plan radiation therapy for cancer of the brain or other tissues
- Guide the passage of a needle used to obtain a tissue sample (biopsy) from the brain
- Assess aneurysms or arteriovenous malformations through a technique called CT angiography. For more information, see the CT Angiography page.
A CT scan of the facial area produces images of a patient’s sinus cavity. The paranasal sinuses are hollow, air-filled spaces located within the bones of the face and surrounding the nasal cavity. They are essentially a system of air channels connecting the nose with the back of the throat. There are four pairs of sinuses, each connected to the nasal cavity by small openings.
CT of the sinuses primarily is used to:
- Detect the presence of inflammatory diseases
- Plan for surgery by defining anatomy or giving further information about tumors of the nasal cavity and sinuses
- Evaluate sinuses that are filled with fluid or thickened sinus membranes
- Help diagnose sinusitis