Preparing for a CT Scan

Wear comfortable, loose-fitting clothing to your exam. You may be given a gown to wear during the scan. 

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 before your scan, 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 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. 

Please bring a list of your current medications:  prescriptions, over the counter medications, and vitamins. 

Women should always inform their physician or technologist if there is any possibility that they are pregnant. 

If your infant or young child is having a spiral CT, there are measures that can be taken to ensure that the test will not cause anxiety for either the child or parent.

Understanding the CT Scan

In many ways CT scanning works very much like other X-ray examinations. X-rays are a form of radiation-like light or radio waves-that can be directed at the body.  Different body parts absorb the X-rays in varying degrees. 

In a conventional X-ray exam, a small burst of radiation is aimed at and passes through the body, recording an image on photographic film or a special image recording plate. Bones appear white on the X-ray, soft tissue shows up in shades of gray and air appears black.

With CT scanning, numerous X-ray beams and a set of electronic X-ray detectors rotate around you, measuring the amount of radiation being absorbed throughout your body. At the same time, the examination table is moving through the scanner, so that the X-ray beam follows a spiral path. A special computer program processes this series of pictures, or slices of the body, to create two-dimensional cross-sectional images, which are then displayed on a monitor. 

CT imaging is sometimes compared to looking into a loaf of bread by cutting the loaf into thin slices. When the image slices are reassembled by computer software, the result is a very detailed multidimensional view of the body's interior.

Refinements in detector technology allow new CT scanners to obtain multiple slices in a single rotation. These scanners, called "Multislice CT" or "multidetector CT," allow thinner slices to be obtained in a shorter period of time, resulting in more detail and additional view capability. 

Modern CT scanners are so fast that they can scan through large sections of the body in just a few seconds. Such speed is beneficial for all patients, especially children, the elderly and critically ill. 

For some CT exams, a contrast material is used to enhance visibility in the area of the body being studied.

Expectations During and After the Scan

Most CT exams are painless, fast and easy. With spiral 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 you have a hard time staying still, are claustrophobic or have chronic pain, you may find a CT exam to be stressful. The technologist or nurse may offer you a mild sedative to help. 

If an intravenous contrast material is used, you will feel a slight prick when the needle is inserted into the vein.  A warm, flushed sensation may be felt during the injection of the contrast materials and a metallic taste in your mouth that lasts for a few minutes.   

Occasionally, patients develop hives and an itch, which can be relieved with medication.  If you become light-headed or experience difficulty breathing, the technologist or nurse should be notified immediately, as it may indicate a more severe allergic reaction. 

When entering the CT scanner, special lights may be used to properly position you, and you may hear slight buzzing, clicking and whirring sounds as the CT scanner moves during the imaging process. 

During the CT scan, you will be alone in the exam room, however, the technologist will be able to see, hear and speak with you at all times. 

With pediatric patients, a parent may be allowed in the room, but will be required to wear a lead apron to prevent radiation exposure. 

After a CT exam, you may return to normal activities. If a contrast material was given, special instructions may follow.

Results

A radiologist, a physician specifically trained to supervise and interpret radiology examinations, will analyze the images and send a signed report to your primary care or referring physician, who will share the results with you.

Benefits vs. Risks

Benefits

• Spinal CT scanning is a rapid procedure and offers an accurate evaluation of bone and most soft tissues. Using the latest equipment, the spine may be displayed in multiple planes and three-dimensional imaging is an option.
• CT scanning is painless, noninvasive and accurate.
• A major advantage of CT is that it is able to provide detailed images of bone, lungs and other soft tissue and blood vessels all at the same time.
• CT examinations are fast and simple; in emergency cases, they can reveal internal injuries and bleeding quickly that helps save lives.
• CT is shown to be a cost-effective imaging tool for a wide range of clinical problems.
• CT may be less expensive than MRI. In addition, it is less sensitive to patient movement.
• CT can be performed if you have an implanted medical device of any kind, unlike MRI.
• CT provides real-time imaging, making it a good tool for guiding minimally invasive procedures such as needle biopsies and needle aspirations of many areas of the body, particularly the lungs, abdomen, pelvis and bones.
• A diagnosis determined by CT scanning may eliminate the need for exploratory surgery and surgical biopsy.
• No radiation remains in a patient's body after a CT examination.
• X-rays used in CT scans usually have no side effects.

Risks

• There is always a slight chance developing from radiation exposure. However, the benefit of an accurate diagnosis outweighs the risk.
• The effective radiation dose from CT imaging is about 10 mSv, which is about the same as the average person receives from background radiation in three years. Background radiation is natural radiation from earth and space.
• Women should always inform their physician or CT technologist if there is any possibility that they are pregnant.
• CT scanning is, in general, not recommended for pregnant women because of potential risk to the baby.
• Nursing mothers should wait for 48 hours after contrast material injection before breast feeding.
• The risk of serious allergic reaction to contrast materials that contain iodine is rare, and radiology departments are well equipped to deal with them.
• Children should have a CT study only if it is essential for making a diagnosis and should not have repeated CT studies unless absolutely necessary.