What is a CAT Scan?
A CAT Scan (CT) uses special x-ray equipment to obtain image data from different angles around the body, and then uses computer processing of the information to show a cross-section of body tissues and organs.
CT is particularly useful because it can show several types of tissue – lung, bone, soft tissue, and blood vessels – with great clarity. Using specialized equipment and expertise to create and interpret CT scans of the body, radiologists can more easily diagnose problems such as cancers, cardiovascular disease, infectious disease, trauma and musculoskeletal disorders.
Common uses of the procedure:
Because it provides detailed, cross-sectional views of all types of tissue, CT is one of the best tools for studying the chest and abdomen. It is often the preferred method for diagnosing different cancers, including lung, liver and pancreatic cancer, since the image allows a physician to confirm the presence of a tumor and to measure its size, precise location, and the extent of the tumor’s involvement with other nearby tissue.
In cases of trauma, CT can quickly help the physician identify injuries to the liver, spleen, kidneys or other internal organs. CT also plays a significant role in the detection, diagnosis and treatment of vascular diseases that can lead to stroke, gangrene or kidney failure.
What does the equipment look like?
The CT scanner is a large, square machine with a hole in the center, something like a doughnut. You will lie still on the table that can move up or down, and slide into and out from the center of the hole. Within the machine, an x-ray tube on a rotating circular frame with a detector on the opposite side moves around your body to produce the images. It may make clicking and whirring noises as the arm moves. The scanner is also equipped with an automated voice instructing the patient to hold their breath when needed.
How is the procedure performed?
The technologist begins by positioning you on the CT table. Your body may be supported by pillows to help you hold still and in the proper position during the procedure. As the study proceeds, the table will move slowly into the opening in the center of the scanner. Depending on the area of your body being examined, the increments of movement may be so small that they are almost undetectable, or large enough that you will feel the sensation of motion.
A CT exam often requires the use of different contrast materials to enhance the visibility of certain tissues or blood vessels. The contrast material may be injected directly into your blood stream, given orally or administered by enema depending on the type of exam. Before the contrast material is administered the technologist will ask whether you have allergies, especially to medications or iodine, and additional medical history. Nursing mothers should wait 24 hours after contrast material is administered before resuming breast-feeding.
What will I experience during the exam?
CT scanning causes no pain, with spiral CT, the need to lie still for any length of time is reduced. For different parts of the body, your preparation will vary. You may be asked to swallow a liquid contrast material, which allows the radiologist to better see the stomach, small bowel, and colon. Your exam may require the administration of the material by enema if the colon is the focus of the study.
Contrast material may also be injected into a vein to better define the blood vessels, internal organs and to accentuate the appearance between normal and abnormal tissues. Some people feel a flush of heat or a metallic taste in the back of the mouth. These sensations usually disappear within a minute or two. Some people may experience a mild itching sensation. If itching persists or accompanied by hives (small bumps on the skin), it can easily be treated with medication.
In very rare cases, a patient may become short of breath or experience swelling in the throat or other parts of the body. These can be indications of a more serious reaction to the contrast material that should be treated promptly, so tell the technologist immediately if you experience these symptoms. Fortunately, with the safety of the newest contrast materials, these adverse effects are very rare. You will be alone in the room during the procedure; however the technologist can see, hear and speak with you at all times. For pediatric patients, a parent (who is not pregnant) may be allowed in the room with the child to alleviate fear, but may be required to wear a lead apron to prevent radiation exposure.
How does the CT Scan work?
In many ways, CT scanning works like other x-ray exams. Very small, controlled amounts of x-ray radiation are passed through the body, and different tissues absorb the radiation at different rates. You might think of it like looking into a loaf of bread by cutting it into thin slices. When the image slices are reassembled by the computer, the result is a very detailed, multidimensional view of the body’s interior.
How should I prepare for the procedure?
You should wear comfortable, loose-fitting clothing for your CT exam. Metal objects can affect the image, so avoid clothing with zippers and snaps. If the CT exam is of the chest or abdomen women will be asked to remove their bra if it has metal clips or under-wires and dress in a gown. You may also be asked to remove hairpins, jewelry, eyeglasses, hearing aides and any removable dental work, depending on the part of your body that is being scanned.
You may be asked not to eat or drink anything for four or more hours prior to your exam. Contrast (liquid drinks) may be given for exams of the abdomen and/or pelvis. Women may be asked to insert a tampon for exams of the pelvic area.
Women should always inform their doctor or x-ray technologist if there is any possibility that they are pregnant.
For some patients a lab test to evaluate your renal (kidney) function may be required prior to the injection of the radiology contrast material.
Patients with a history of any of the following will require a lab test within 30 days prior to the exam.
1. Age 70 or older
2. History of kidney/renal disease, single kidney, kidney/renal surgery (kidney removed, tumor or transplant)
3. History of or taking medication for hypertension (high blood pressure)
4. History of or taking medication for hyperureicemia (gout, or high levels of uric acid in blood stream)
5. Taking medication containing Metformin (for diabetes)
6. History of liver disease, liver transplant, or impending liver transplant.
Who interprets the CT Scan?
A radiologist, who is a physician experienced in CT and other imaging examinations, will analyze the images and send a signed report with his/her interpretation to your primary care physician. Your physician’s office will inform you how to obtain the results.