Computed axial tomography, often called a CT or CAT scan, is used to image the human body. The CT scan uses x-rays and computers to produce a cross-sectional image of the body. Imagine the body as a loaf of bread and you are looking at one end of the bread. As you remove each slice of bread, you can see the entire surface of that slice from the crust to the center. The body is seen on CT scan slices in a similar fashion from the skin to the central part of the body being examined.
When these levels are further added together, a three-dimensional picture of an organ or abnormal body structure can be obtained. A series of such images can create a multidimensional view of the body.
A CT scan can be performed on most parts of the body. It has the advantage of being able to distinguish more tissue densities than conventional x-rays and allows us to visualize tissues, muscles, organs, blood vessels, and bones.
Why a CT Scan is Performed
Just as with x-rays, there are many uses for CT scans. The following are some more common uses:
- Diagnose problems such as cancers, cardiovascular disease, infectious disease, trauma and musculoskeletal disorders.
- Assessment of a body part’s structure or shape
- Diagnosis of trauma or injury
- Diagnosis of vascular disease
- Aid to planning particular surgeries
- Visual aid to certain surgical procedures such as biopsy or needle aspiration
How to Prepare for a CT Scan
Certain exams require a special dye, called contrast, to be delivered into your body before the test starts. Contrast helps certain areas show up better on the x-rays.
Let your health care provider know if you have ever had a reaction to contrast. You may need to take medicines before the test in order to avoid another reaction.
Contrast can be given several ways, depending on the type of CT being performed.
- It may be delivered through a vein (IV) in your hand or forearm.
- You might drink the contrast before your scan. When you drink the contrast depends on the type of exam being done. The contrast liquid may taste chalky, although some are flavored. The contrast passes out of your body through your stools.
- Rarely, the contrast may be given into your rectum using an enema.
If contrast is used, you may also be asked not to eat or drink anything for 4 to 6 hours before the test.
Before receiving IV contrast, tell your health care provider if you take the diabetes medication metformin (Glucophage). People taking this medicine may need to stop temporarily. Also let your provider know if you have any problems with your kidneys. The IV contrast can worsen kidney function.
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.
CT Scan Safety
All of our equipment is maintained by highly trained service engineers and meets or exceeds the operating specifications set forth by the manufacturers and the federal government.
If you are pregnant or think you might be, please tell the staff before the test. As with other medical procedures, x-rays are safe when used with care. Radiologists and CT technologists have been trained to use the minimum amount of radiation necessary to obtain the needed results. The amount of radiation used in most examinations is very small and the benefits may greatly outweigh the risk of harm.
Before you have a CT scan, tell your doctor if you:
- Are breast-feeding. You will need to use formula for 1 to 2 days if you are given contrast so that you do not pass the contrast to your baby. You should discard any breast milk you collect during this time.
- Are allergic to any medicines, including iodine dyes.
- Have a heart condition, such as heart failure.
- Have diabetes or take metformin (Glucophage) for your diabetes.
- Have had kidney problems.
- Have asthma.
- Have had thyroid problems.
- Have had multiple myeloma.
- Have had an X-ray test using barium contrast material (such as a barium enema) or have taken a medicine that contains bismuth (such as Pepto-Bismol) in the past 4 days. Barium and bismuth show up on X-ray films and make it difficult to see the picture clearly.
- Become very nervous in small spaces. You need to lie still inside the CT scanner, so you may need a medicine (sedative) to help you relax.
CT Scan Results
All CT scans are read by Wake Forest Baptist radiologists trained in CT imaging and dedicated to the specific body part scanned. They will read your exam within 24 hours and results will be sent to the doctor that ordered your exam. Your doctor will then discuss the results with you and what they mean in relation to your health.