What Is a Cat Scan?

By Nicole Harms

If your doctor has ordered a CAT scan, you are facing one of the most common diagnostic procedures in modern medicine. CT scans, as they are properly called, are painless, non-invasive medical tests that allow doctors to see inside the body with more clarity than is possible with a traditional x-ray.

Understanding CT Scans

A CT scan--the letters stand for "computerized tomography"--is a medical diagnostic test that combines x-rays and computerized technology to produce cross-sectional images of an area inside the body. The area being studied in the scan could be an internal organ, blood vessels, soft tissue or bones. Doctors use CT scanning technology when they need more detail and clarity than is available with a traditional x-ray. Physicians use the images to diagnose and prescribe treatment for medical conditions and injuries.


Doctors often choose CT scans to diagnose cancer, particular cancer in the lungs, liver or pancreas. The scans allow the doctor to locate and measure the cancer very precisely. Medical professionals also use these scans to study the chest, abdomen and pelvis for other non-cancerous conditions and injuries. Spinal problems and injuries to the skeleton that do not show up well on x-ray are shown on CT scans. Because CT scans can show blood vessels in great detail, doctors use them to detect and diagnose types of vascular disease.

The Procedure

When facing a CT scan, you will recline on an examination table, and the technician will use pillows or straps to help keep your body in the proper position during the scan. You need to remain still during the procedure. Sometimes contrast material is used to show the digestive tract or your veins and arteries. This is swallowed or administered through an IV or enema. The scanner looks like a large box with a hole in the middle. The table moves though that hole so the scanner can send the x-rays to the targeted area of your body. The average CT scan takes 30 minutes.

CT Scans vs. Traditional X-Rays

A CT scan is different from a traditional x-ray in that during a CT scan numerous x-ray beams are sent into the body, while electronic x-ray detectors rotate around the body, measuring the amount of radiation the body absorbs. In addition, the movement of the table through the scanner creates a spiral path for the x-ray beam, which allows the computer to create two-dimensional cross-section scans. Traditional x-rays send x-ray beams through the body onto a photographic film or plate on the other side. This produces a one-dimensional image of the body, showing bones, fluid, soft tissue and air in various shades of black, white and gray.

Risks and Benefits

CT scans involve radiation, and excessive exposure to radiation can increase cancer risk. Radiation does pose a risk of birth defects in unborn babies, so pregnant women should not have these scans without consulting with their obstetricians. Allergic reactions to the contrast materials used with some CT scans can occur. Breastfeeding mothers need to wait 24 hours after receiving contrast materials before resuming their nursing schedule. Some benefits of CT scanning include giving doctors a noninvasive, pain-free way to diagnose many conditions. Results from CT scans are received quickly, making them ideal for emergency diagnoses.

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