A CT scan is a computer-assisted X-ray that takes pictures of the body in slices, just like a loaf of bread.
GOT A MINUTE?
Demystifying radiologic testing
Diagnosing illness has become a more exacting process
A broken bone. A suspected stroke. Injuries sustained in an accident. A pregnancy. A bad heart valve. All these medical situations require some form of radiologic testing.
Thirty or 40 years ago the only way to see inside the body was to do plain X-rays, which had real limitations in some instances. Now the availability of so many different types of radiologic testing makes diagnosing illnesses and conditions a much more exacting process.
If you are in your mid-20s or older, chances are good that you have had some form of radiologic testing in your lifetime. Maybe you have wondered exactly what is going on when these tests are performed.
Let’s take a look at some of these tests and see if we can demystify them.
The most common tests that fall under the category of radiology are X-rays, ultrasounds, CT scans, MRI scans and nuclear scans. Some of these tests require that a substance be injected or ingested to help the structures that are being studied show up better.
X-rays are the most common and usually the first imaging tests used to take a look inside the body. Low doses of radiation are used to project the image of the body part in question onto film that is sensitive to the radiation. Different body parts have different densities, making them show up on the film in varying degrees of light and dark. For example, bones, which are quite dense, show up white, while the soft tissue structures around them are more gray. Air-filled areas like the lungs show up as black because there are no structures to impede the rays as they travel to the film.
Plain X-rays are commonly used to detect broken bones, lung abnormalities like pneumonia or tumors, and problems with the digestive system. Certain types of X-rays of the digestive tract require that the person drink some fluid (called contrast) that will show up brightly on the film, highlighting structures that are more difficult to see on a plain X-ray. Contrast material can also be injected into blood vessels so that they show up on the films, when otherwise they are barely visible at all.
Sometimes an X-ray can’t show enough detail for the doctor to make a diagnosis. This is when a CT scan or an MRI becomes a valuable tool for discovering what is going on. CT stands for computed tomography; it’s an X-ray that is computer assisted to take pictures of the body in slices, just like a loaf of bread. Then the individual slices can be studied one by one in order to locate problems deep inside the body. A CT scan is often used to diagnose trauma to the spine, pelvis, head or abdominal structures. Contrast can be used in CT scans to make the images more defined.
If a CT scan can’t give enough information to the doctor, an MRI (magnetic resonance imaging) might be used in diagnosing the condition. An MRI takes very high-resolution, cross-sectional pictures of the body, but it does so without using radiation. The machine creates a magnetic field around the person being scanned and then pulses radio waves towards the area being studied. These radio waves cause the tissues in the body to vibrate. This is not able to be felt by the person being scanned. The different body tissues vibrate at different rates. This information is sent to the computer within the machine that can use these vibration rates to make pictures of the structures. Conditions that are better seen with an MRI are torn ligaments and cartilage, torn rotator cuffs, herniated disks, problems with pelvic structures and other soft-tissue areas.
If you are unfortunate enough to be in a position to need any of these diagnostic tests, now you will know a bit about what is going on during the process.
In the following weeks, this column will look at some other imaging tests and then move on into other testing procedures.
Pam Maxson is a health educator at Noyes Health is Dansville. If you have questions or suggestions for future articles, she can be reached at firstname.lastname@example.org or 335-4327.