What Does a CT Scan Show? Here’s the Difference Between CT scan vs. X-Ray
Key takeaways:
CT scans and X-rays use high-energy waves to form images of organs and structures inside the body.
Each test has its own advantages and disadvantages. The imaging test a healthcare provider recommends depends on the specific symptoms and conditions.
CT scans provide more complete and detailed images than X-rays. But they’re also more expensive and create more radiation exposure. A healthcare provider can help choose the right test in each circumstance.
Imaging tests look at organs and structures inside the body. CT scans and X-rays are two common forms of imaging tests.
Healthcare providers use these tests to look for things like broken bones and bleeding and to figure out what might be causing a symptom like pain or fever. And sometimes they’re used as screening tests to catch diseases in an earlier, more treatable phase.
If a healthcare provider recommends a certain imaging test, it’s helpful to know why. And it’s useful to understand the difference between them.
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What is an X-ray?
X-rays are high-energy waves that can pass through the body. In healthcare, X-rays are used to form images of the structures inside the body. X-rays have been used as imaging tests for more than a century. Since the early days, many new techniques have improved the X-ray images of different parts of the body.
Dense body parts show up lighter on an X-ray. And less dense parts are darker. So X-rays are helpful for looking at things like bone. They’re also useful for looking at areas that contain air, like the lungs. This makes it easier to see something that doesn’t belong, like a fracture, tumor, or infection.
To have an X-ray, you may sit, stand, or lie down. It depends on the type of exam. An X-ray takes a two-dimensional picture. So images may be taken from different angles or in a few positions. X-rays are painless and usually take just a few minutes.
Comparing imaging tests: CT scans and MRIs are both used to take a closer look inside the body. Learn more about the differences between the tests, including the pros and cons of each.
Covering X-ray costs: Most insurance plans cover X-rays, though you might have some out-of-pocket costs. Here’s what you can expect to pay, and what factors might affect the price.
Getting answers: Imaging tests can help identify causes for many different symptoms, including back pain. Three people share their experiences with a slipped disc and how they were diagnosed.
What is a CT scan?
A CT scan (computed tomography) also uses X-rays, but it directs the X-rays in a circle around the body. That creates a detailed picture of the area being examined. A CT scan makes thin, cross-section images of an area of the body like the head, chest, or abdomen.
Healthcare providers can look at these images one by one and as a whole. That gives a lot of information about what may or may not be going on inside.
For a CT scan, you lie down on a motorized table in a hospital or outpatient center. The table moves through the round CT scanner, which takes images of a specific body part. Some CT scans need contrast dye to see areas more clearly. The contrast dye is given by mouth or in an IV before the scan.
A CT scan is painless and usually takes less than an hour. If no contrast dye is needed, it might be just a few minutes. You’re not enclosed in a CT scanner, and there’s not much noise. And a CT technician is always a few steps away to give you instructions or answer questions.
The pros and cons of an X-ray
Healthcare professionals recommend certain imaging tests to check for different conditions. Sometimes more than one test may be needed. At other times, there may be a few options for what kind of imaging is done. Let’s first look at the pros and cons of X-rays and then CT scans.
Pros
Here are some reasons an X-ray may be a good option:
An X-ray can be a good first test to look for tumors, injuries, fractures, or infections.
X-rays are especially helpful in looking at structures that are very dense (like bone) or not dense (like lungs).
X-rays are quick, less expensive, and create less radiation exposure.
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Cons
An X-ray isn’t always the best imaging choice. Here are some downsides:
X-rays provide less detail, especially for soft tissues and internal organs.
The images may be less complete and show a smaller area.
More imaging tests may be needed if X-rays aren’t enough for diagnosis or treatment.
The pros and cons of a CT scan
CT scans have some clear advantages over X-rays, but they aren’t perfect. Let’s take a closer look.
Pros
Here are some pros of a CT scan:
CT scans provide clearer images.
CT scan images give a more complete view of organs and body structures. They can be used to diagnose disease or plan treatment.
A CT scan may eliminate the need for surgery to explore something like a tumor or injury.
Even though they take a little longer than an X-ray, CT scans are relatively quick and painless tests.
Cons
CTs scan carry some risks and a higher cost:
Some CT scans may need oral or IV contrast dye. This comes with a risk of kidney problems or allergic reactions.
CT scans cause more radiation exposure than X-rays. This is more of a risk for children and during pregnancy or when someone needs repeated CT scans.
A CT scan may cost up to 10 times as much as an X-ray. This is a particular concern for people without insurance, or when insurance doesn’t cover the cost.
How do you know what kind of imaging test you need?
A healthcare provider will recommend an imaging test based on your symptoms or health concerns. But sometimes there may be more than one option.
The American College of Radiology has criteria to recommend different imaging tests. And it’s important to know that imaging is not always required to make a diagnosis. Often, a good history and physical examination with a trained healthcare provider are all that’s needed. That can be enough to make a diagnosis and start a treatment plan.
X-ray uses
X-rays are used to:
Diagnose bone fractures and dislocations
Check for pneumonia, tuberculosis, and other lung problems
Check for foreign objects
Diagnose or follow conditions in people who can’t use contrast dye
Diagnose problems with the teeth, like cavities
Screen for breast cancer (with a mammogram)
There’s also a special type of X-ray called fluoroscopy. It uses oral or IV contrast to take a live picture of the heart, blood vessels, intestines, or other organs.
CT scan uses
CT scans are used to:
Evaluate the size and qualities of tumors and other masses
Look for blood clots or bleeding
Check for injury, infection, fluid, or blockages
Diagnose strokes
Screen for lung cancer in people who smoke
Screen for cardiovascular disease (this is a special type of CT scan done for some people with certain risk factors)
Other imaging tests
Other types of imaging tests include:
Magnetic resonance imaging (MRI and MRA)
Nuclear medicine tests, such as bone scans, thyroid scans, and some cardiac stress tests
Positron emission tomography (PET scan)
The bottom line
CT scans and X-rays are two of the most common types of imaging tests in healthcare. CT scans provide more detailed images of internal organs. But they also have more radiation. Even though X-rays are less detailed, they have less radiation. And the’re still good tests for certain conditions. If you’re curious why you’re getting one test over the other, don’t hesitate to ask your healthcare provider. They’re there to make sure you get the right test.
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References
American Cancer Society. (2015). CT scan for cancer.
American College of Radiology. (n.d.). Appropriateness criteria.
American Heart Association. (2023). Coronary artery calcium (CAC) test.
Choosing Wisely. (n.d.). Advanced the national dialogue.
Columbia Surgery. (n.d.). History of medicine: Dr. Roentgen’s accidental x-rays.
National Institute of Biomedical Imaging and Bioengineering. (2022). Computed tomography (CT).
National Institute of Biomedical Imaging and Bioengineering. (2022). X-rays.
U.S. Food and Drug Administration. (2023). Computed tomography (CT).
U.S. Food and Drug Administration. (2023). Fluoroscopy.
