Computed tomography (CT) scanning, also referred to as computerized axial tomography (CAT) scanning, is an imaging procedure that uses x-rays to create pictures that are cross-sections of parts of the body.
How Does a CT Scan Work?
A combination x-ray source and detector device located inside the machine continually rotates around the patient. Each rotation last approximately one second. The x-ray source portion creates a thin, fan-shaped beam of rays that penetrate the section of the patient’s body that is being scanned. The detector portion, which is on the opposite from the x-ray source, makes snapshots of the x-rays that are passing through the patient’s body. Many different images from a variety of angles are gathered during one complete rotation. After each rotation, the image data are transmitted to a computer that reconstructs all of the individual snapshots into one or more cross-sectional images of the area being scanned.
Certain CT scans require contrast material that heightens the clarity of the image. The type of contrast used in this kind of imaging scan can contain iodine. Patients should inform their doctor of any known allergy to the contrast materials, also called dyes, because the doctor may be able to prescribe medication to decrease the risk of an allergic reaction.
What are the Benefits Associated with this Type of Imaging Scan?
- Non-invasive CT scans offer some important advantages that are different from those offered by other diagnostic tests:
- They can create images of bone, soft tissue and blood vessels simultaneously.
- The images they provide are very detailed pictures of many types of tissues and organs.
- They are an effective tool for diagnosing a wide spectrum of abnormalities and conditions.
- They do not have the same sensitivity to patient movement as an MRI.
- Patients with implanted medical devices of any kind can undergo a CT scan.
- They create real-time images that are an important tool for guiding needle biopsies and needle aspirations.
- A CT scan may eliminate the need for exploratory surgery and/or surgical biopsy.
- There is no residual radiation in a patient’s body after a CT scan
- The type of x-rays used in CT scans has no immediate after effects.
What are the Risks?
The Food and Drug Administration has prepared the following list of risks that are associated with this type of scan:
- An increased lifetime risk of cancer due to x-ray radiation exposure.
- Possible allergic reactions or kidney failure due to contrast agent, or “dye” that may be used in some cases to improve visualization.
- The need for additional follow-up tests after receiving abnormal test results or to monitor the effect of a treatment on disease, such as to monitor a tumor after surgical removal. Some of these tests may be invasive and present additional risks.
- The agency also cautions that , “Under some rare circumstances of prolonged, high-dose exposure, x-rays can cause other adverse health effects, such as skin reddening (erythema), skin tissue injury, hair loss, cataracts, and potentially, birth defects (if scanning is done during pregnancy).”