CT (Computed Tomography) Scanning — also called CAT scanning — is a noninvasive medical test that helps physicians diagnose and treat medical conditions. CT takes the concept of conventional X-ray imaging to a new level by combining special X-ray equipment with sophisticated computers to produce multiple images or pictures of the inside of the body. CT scans of internal organs, bone, soft tissue, and blood vessels provide greater clarity and reveal more details than regular X-ray exams.
Instead of finding the outline of bones and organs, the CAT scan’s X-ray beam moves all around the patient, scanning from hundreds of different angles. The computer takes all this information and puts together a three-dimensional image of the body. Doctors can even examine the body one narrow slice at a time to pinpoint specific areas of concern.
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 take out any 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. Your examination may require oral preparation or intravenous contrasts given at the time of your exam. You should inform your physician of any medications you are taking and if you have any allergies. If you have a known allergy to any contrast material, or “dye,” your doctor may prescribe medications to reduce the risk of an allergic reaction.
Women should always inform their physician and the CT technologist if there is any possibility that they may be pregnant due to radiation exposure.
What to Expect
The CT Scanner machine looks like a giant donut tipped on its side. The patient lies down on a platform, which slowly slides through the hole in the machine. The machine records X-ray slices across the body in a spiral motion. The computer varies the intensity of the X-rays in order to scan each type of tissue with the optimum power.
CT exams are generally painless, fast, and easy. 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 experience chronic pain, you may find a CT exam stressful. You may be asked to hold your breath during the scanning. The scanner or a technologist may talk to you throughout your exam. Any motion, whether breathing or body movements, can lead to artifacts on the images. This is similar to the blurring seen on a photograph taken of a moving object.
If an intravenous contrast material is used, you will feel a slight pin-prick when the needle is inserted into your vein. You may have a warm, flushed sensation during the injection of the contrast materials and a metallic taste in your mouth that lasts for a few minutes. Some patients may experience a sensation like they have to urinate, but this quickly subsides.
When you enter the CT scanner, special lights may be used to ensure that you are properly positioned. With modern CT scanners, you will hear only slight buzzing, clicking, and whirring sounds as the CT scanner revolves around you during the imaging process. You will be alone in the exam room during the CT scan. However, the technologist will be able to see, hear, and speak with you at all times.
After the patient passes through the machine, the computer combines all the information from each scan to form a detailed image of the body. It is not usually necessary to scan the entire body. More often, doctors will scan only a small section. Since they examine the body slice by slice, CAT scans are more comprehensive than conventional x-rays.
After a CT exam, you can return to your normal activities. If you received contrast material, you may be given special instructions. You may be asked to refrain from taking metformin following your scan.
Advantages of CT Scanning
CT scanning is painless, noninvasive, accurate, and normally only takes minutes to complete. A major advantage of CT is its ability to image bone, soft tissue, and blood vessels all at the same time. Unlike conventional X-rays, CT scanning provides very detailed images of many types of tissue. In emergency cases, it can reveal internal injuries and bleeding quickly enough to help save lives. No radiation remains in a patient’s body after a CT examination, and unlike MRI, it can be performed if you have an implanted medical device of any kind.
CT imaging 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.
Common uses of CT include:
- Studying the chest, abdomen, and pelvis
- Diagnosing many different cancers, including lung, liver, and pancreatic cancer, since the images allow physicians to confirm the presence of tumors
- Detecting, diagnosing, and treating vascular diseases that can lead to stroke, kidney failure, or even death
- Diagnosing and treating spinal problems and injuries to the hands, feet, and other skeletal structures, because it can clearly show even very small bones, as well as surrounding tissues such as muscle and blood
- Diagnosing kidney stones
Three important applications of CT technology offered by ProScan are:
Cardiac CT for Calcium Scoring:
A cardiac CT scan for coronary calcium is a noninvasive way of obtaining information about the presence, location, and extent of calcified plaque in the coronary arteries — the vessels that supply oxygen-containing blood to the heart muscle. Calcified plaque results when there is a build-up of fat and other substances under the inner layer of the artery.
This material can calcify, which signals the presence of atherosclerosis, a disease of the vessel wall, also called coronary artery disease (CAD). People with CAD have an increased risk of heart attacks. Over time, progression of plaque build-up can narrow the arteries or even close off blood flow to the heart. The result may be chest pain, also sometimes called “angina”, or even a heart attack. The findings on cardiac CT are expressed as a calcium score. Another name for this test is coronary artery calcium scoring.
Cardiac CT Angiography (CCTA):
After a calcium score is completed, it is determined whether or not a CCTA should be conducted. Because calcium is a marker for coronary artery disease (CAD), the amount of calcium detected on a cardiac CT scan is a helpful prognostic tool. Coronary computed tomography angiography (CCTA) is a heart imaging test that helps determine if fatty or calcium deposits have narrowed a patient’s coronary arteries. CCTA is the next step in identifying CAD because it not only detects calcified plaque, but also identifies the soft or vulnerable plaque within the artery walls. For more information on CCTA, click here.
CT Colonography (CTC):
Also called “virtual colonoscopy,” this noninvasive alternative to conventional colonoscopy uses sophisticated software and an advanced 64-slice scanner to create two- and three-dimensional images of the colon. A CTC is faster, easier, and more comfortable for the patient than a conventional colonoscopy. For more information on CTC at ProScan, click here.
Many CT procedures do not require the use of contrast; however, some exams require the use of injectable contrast or dyes. If contrast material is used, it will be swallowed, injected through an intravenous (IV) line, or administered by enema (for virtual colonoscopy only).