The patient lies down on a platform, which slowly moves through the hole in the machine. The X-ray tube is mounted on a movable ring around the edges of the hole. The ring also supports an array of X-ray detectors directly opposite the X-ray tube. A motor turns the ring so that the X-ray tube and the X-ray detectors revolve around the body. Each full revolution scans a narrow, horizontal " slice " of the body. The control system moves the platform farther into the hole so the tube and detectors can scan the next slice.
In this way, 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. 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's not usually necessary to scan the entire body, of course. More often, doctors will scan only a small section.
Since they examine the body slice by slice, from all angles, CAT scans are much more comprehensive than conventional X-rays. Today, doctors use CAT scans to diagnose and treat a wide variety of ailments, including head trauma, cancer and osteoporosis. They are an invaluable tool in modern medicine. For much more information about CAT scan machines and other medical scanners, check out the links on the next page. Sign up for our Newsletter! Mobile Newsletter banner close. Mayo Clinic does not endorse companies or products.
Advertising revenue supports our not-for-profit mission. This content does not have an English version. This content does not have an Arabic version. Overview CT scan Open pop-up dialog box Close. CT scan A CT scan can be used to visualize nearly all parts of the body and is used to diagnose disease or injury as well as to plan medical, surgical or radiation treatment. Request an Appointment at Mayo Clinic. Share on: Facebook Twitter. Show references Radiation-emitting products: Computed tomography CT.
Food and Drug Administration. Accessed Jan. Lee C, et al. Radiation-related risks of imaging. Computed tomography CT — Body. Radiological Society of North America. Accessed Feb. McCollough C, et al. Answers to common questions about the use and safety of CT scans. Mayo Clinic Proceedings. ACR-SPR practice parameter for imaging pregnant or potentially pregnant adolescents and women with ionizing radiation.
Reston, Va. Mayo Clinic Press Check out these best-sellers and special offers on books and newsletters from Mayo Clinic. You may need a follow-up exam. If so, your doctor will explain why. Sometimes a follow-up exam further evaluates a potential issue with more views or a special imaging technique.
It may also see if there has been any change in an issue over time. Follow-up exams are often the best way to see if treatment is working or if a problem needs attention. There is no conclusive evidence that radiation at small amounts delivered by a CT scan causes cancer. Large population studies have shown a slight increase in cancer from much larger amounts of radiation, such as from radiation therapy.
Thus, there is always concern that this risk may also apply to the lower amounts of radiation delivered by a CT exam. When a CT scan is recommended by your doctor, the expected benefit of this test outweighs the potential risk from radiation. You are encouraged to discuss the risks versus the benefits of your CT scan with your doctor or radiologist, and to explore whether alternative imaging tests may be available to diagnose your condition.
Soft-tissue details in areas such as the brain, gallbladder , internal pelvic organs, and joints such as knees and shoulders can often be better evaluated with magnetic resonance imaging MRI. In pregnant women, while CT can be performed safely, other imaging exams not involving radiation, such as ultrasound or MRI, are preferred but only if they are likely to be as good as CT in diagnosing your condition.
A person who is very large may not fit into the opening of a conventional CT scanner. Or, they may be over the weight limit—usually pounds—for the moving table. Please type your comment or suggestion into the text box below. Note: we are unable to answer specific questions or offer individual medical advice or opinions. Some imaging tests and treatments have special pediatric considerations.
The teddy bear denotes child-specific content. Please contact your physician with specific medical questions or for a referral to a radiologist or other physician. To locate a medical imaging or radiation oncology provider in your community, you can search the ACR-accredited facilities database.
This website does not provide cost information. The costs for specific medical imaging tests, treatments and procedures may vary by geographic region. Web page review process: This Web page is reviewed regularly by a physician with expertise in the medical area presented and is further reviewed by committees from the Radiological Society of North America RSNA and the American College of Radiology ACR , comprising physicians with expertise in several radiologic areas.
Outside links: For the convenience of our users, RadiologyInfo. Toggle navigation. What is CT Scanning of the Body? What are some common uses of the procedure? How should I prepare? What does the CT equipment look like? How does it work How is the procedure performed? What will I experience during and after the procedure? Who interprets the results and how do I get them? What are the benefits vs.
What are the limitations of CT Scanning of the Body? Which test, procedure or treatment is best for me? CT imaging is: one of the fastest and most accurate tools for examining the chest, abdomen and pelvis because it provides detailed, cross-sectional views of all types of tissue. It's considered the best method since the image allows a physician to confirm the presence of a tumor, measure its size, identify its precise location and determine the extent of its involvement with other nearby tissue.
CT is commonly used to assess for pulmonary embolism a blood clot in the lung vessels as well as for aortic aneurysms. In pediatric patients, CT imaging is often used to evaluate:.
How does it work In many ways, a CT scan works like other x-ray exams. How is the procedure performed? Benefits CT scanning is painless, noninvasive, and accurate. 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 as well as the lungs, bones, and blood vessels. CT exams are fast and simple.
In emergency cases, they can reveal internal injuries and bleeding quickly enough to help save lives. CT has been shown to be a cost-effective imaging tool for a wide range of clinical problems. CT is less sensitive to patient movement than MRI. CT imaging provides real-time imaging, making it a good tool for guiding needle biopsies and needle aspirations.
This is particularly true of procedures involving the lungs, abdomen, pelvis, and bones. A diagnosis via CT scan may eliminate the need for exploratory surgery and surgical biopsy. No radiation remains in a patient's body after a CT exam. The x-rays used for CT scanning should have no immediate side effects.
Risks There is no conclusive evidence that radiation at small amounts delivered by a CT scan causes cancer. The radiation dose for this procedure varies. Women should always tell their doctor and x-ray or CT technologist if there is any chance they are pregnant.
See the Safety in X-ray, Interventional Radiology and Nuclear Medicine Procedures page for more information about pregnancy and x-rays. Doctors do not generally recommend CT scanning for pregnant women unless medically necessary because of potential risk to the unborn baby. IV contrast manufacturers indicate mothers should not breastfeed their babies for hours after contrast material is given.
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