What is Computed Tomography?
Computed tomography, or CT, scanning is a popular and effective way of examining any part of the body to detect the presence or absence of disease. It is extremely useful in the evaluation of acute injuries to the head, chest, abdomen, spine and pelvis. It is a valuable tool for cancer patients in determining the size and location of tumors as well as response to treatment. Many new uses of computed tomography have been developed such as detecting kidney stones without the use of injected contrast material ("x-ray dye"), diagnosing appendicitis, as well as special studies of the blood vessels that don't require the surgical placement of a catheter into the blood vessel.
A Radiological Technologist with special training in computed tomography will perform your CT scan. At the start of the procedure the technologist will explain the procedure to you and answer any questions that you have. The technologist will operate the CT scanner from a separate control room but remain in contact with you using a two-way way intercom and watching you through an observation window. To begin the study you will lay on a table connected to the CT scanner. The part of your body being scanned will be positioned in the middle of the large, doughnut-shaped scanner.
Present day scanners have a wide opening that does not feel confining, so you should not feel claustrophobic. The machine will not touch you and you will not feel the x-rays.
Some CT scans require the use of an iodine contrast material, "x-ray dye". The contrast material is used to highlight certain body tissues and structures. One type is given prior to the exam by mouth (usually for abdomen or pelvis scans) to define the intestines. A different contrast material is given by I.V. injection and is used to enhance structures of the body and improve the detection of abnormalities.
During the CT scan, a thin beam of x-rays circles completely around the body, collecting a 360-degree view of the area being examined. This information is fed into a computer system that produces a two dimensional cross sectional "slice" of a portion of the body. Multiple slices are taken to cover the area of the body to be examined. These studies enable the radiologist to see structures inside the body, which makes diagnosis and treatment more accurate.
Is the exam safe?
Millions of CT exams are done every year in the United States. The x-rays used involve a small dose of radiation.
Efforts are always being made to reduce the amount of radiation in these studies and are a special concern for children and women of childbearing age due to risk to a fetus. Generally the small risks of the radiation are outweighed by the potential benefits of the information gained by the study.
Intravenous iodine contrast material is often used depending on the type of exam. These contrast agents are generally safe, but, like all medications, side effects can occur. The incidence of side effects has decreased considerably over the years as newer contrast medicines have been developed. However, a small percent of patients may be allergic to the intravenous agent.
Allergic reactions are usually mild (itching, flushing) but occasionally may be severe. If you have had allergic reactions to these agents before, or if you have asthma or multiple allergies, you may be at higher risk for a reaction. Let your doctor know if you have any of these conditions that would increase your risk.
Iodine contrast can also rarely cause kidney toxicity in people with certain medical conditions, which include but are not limited to: kidney failure, diabetes, multiple myeloma, severe dehydration, hyperuicemia (seen with gout), and heart failure. If you fall into one of these categories, or if you are over age 60, a blood test will be needed prior to the study to measure your kidney function.
What should I wear?
For some of the scans you will be asked to change into a gown. Wear something that is comfortable and easy to remove.
What To Expect?
Patients are placed on a movable table, and the table is slipped into the center of a large donut-shaped machine which takes the x-ray images around the body. The actual procedure can take up to a half an hour. If specific tests, biopsies, or intervention are performed by the radiologist during CT scanning, additional time and monitoring may be required. It is important during the CT scan procedure that the patient minimize any body movement by remaining as still and quiet as is possible. This significantly increases the clarity of the x-ray images. The CT scan technologist tells the patient when to breathe or hold his/her breath during scans of the chest and abdomen. If any problems are experienced during the CT scan, the technologist should be informed immediately. The technologist directly watches the patient through an observation window during the procedure and there is an intercom system in the room for added patient safety.
CT scans have vastly improved the ability of doctors to diagnose many diseases earlier in their course and with much less risk than previous methods. Further refinements in CT scan technology continue to evolve which promise even better picture quality and patient safety. Newer CT scans called "spiral" or "helical" CT scans can provide more rapid and accurate visualization of internal organs. For example, many trauma centers are using these scans to more rapidly diagnose internal injuries after serious body trauma.
How long will it take?
Allow approximately 30 minutes for this exam, though most of this time is preparatory.
The amount of time the machine is actually scanning is usually less than a minute.
What can I expect after the exam?
You should be able to return to your normal activities.
Why are CT scans performed?
CT scans are performed to analyze the internal structures of various parts of the body. This includes the head, where traumatic injuries, (such as blood clots or skull fractures), tumors, and infections can be identified. In the spine, the bony structure of the vertebrae can be accurately defined, as can the anatomy of the intervertebral discs and spinal cord. In fact, CT scan methods can be used to accurately measure the density of bone in evaluating osteoporosis.
Occasionally, contrast material (an x-ray dye) is placed into the spinal fluid to further enhance the scan and the various structural relationships of the spine, the spinal cord, and its nerves. CT scans are also used in the chest to identify tumors, cysts, or infections that may be suspected on a chest x-ray. CT scans of the abdomen are extremely helpful in defining body organ anatomy, including visualizing the liver, gallbladder, pancreas, spleen, aorta, kidneys, uterus, and ovaries. CT scans in this area are used to verify the presence or absence of tumors, infection, abnormal anatomy, or changes of the body from trauma.
The technique is painless and can provide extremely accurate images of body structures in addition to guiding the radiologist in performing certain procedures, such as biopsies of suspected cancers, removal of internal body fluids for various tests, and the draining of abscesses which are deep in the body. Many of these procedures are minimally invasive and have markedly decreased the need to perform surgery to accomplish the same goal.
This procedure is performed at our Woodlands Imaging and 1960 Digital Imaging locations.