A computed tomography (CT or CAT) scan allows doctors to see inside your body. It uses a combination of X-rays and a computer to create pictures of your organs, bones, and other tissues. It shows more detail than a regular X-ray.
You can get a CT scan on any part of your body. The procedure doesn't take very long, and it's painless.
What is a CT scan machine?
The CT scan machine is an imaging device that uses a motorized X-ray to take three-dimensional (3D) digital images.
There are several important parts of a CT scan machine. You lie on a movable table and will slide through the center of a gantry. That is the ring-shaped part of the scanner where the X-ray tube and digital X-ray detectors are. The detectors are opposite the X-ray source. When they capture the X-rays, the detectors send the information to a computer. The computer turns the data into detailed images.
CT scan vs. MRI
A CT scan and MRI are both imaging machines used to help doctors see inside your body. For both of these tests, you’ll lie on a moving table that passes through a doughnut-shaped machine.
A CT scan uses X-rays to image the body. An MRI uses radio waves and a powerful magnet to create similar images. CT scans are helpful in showing where things are – where one organ ends and another begins, for instance. An MRI is geared toward showing normal and abnormal tissue.
CT scans are often used to find cancer, bone fractures, internal bleeding, blood clots, and injuries to the spine and brain. An MRI shows certain diseases that a CT scan can’t. For instance, uterine, prostate, and certain liver cancers are hard to see on a CT scan. Also, an MRI is used to diagnose injuries to the soft tissues or joints and injury to organs like the heart, brain, and digestive organs.
PET scan vs. CT scan
A positron emission tomography (PET) scan is an imaging tool, like a CT scan and MRI, that produces images of your organs and tissues. But it works differently. In a PET scan, you’re injected with a safe radioactive chemical called a radiotracer. After the radiotracer has had a chance to get into your bloodstream, cells, and tissues, you’ll lie on a moving table, similar to one for a CT scan. In places where your body has increased metabolic activity, more of the radiotracer is absorbed. The scan picks that up to show areas where something may be wrong, such as heart disease, cancer, or a brain disorder. A PET scan is able to find cellular changes in your body in real time (even before a CT scan or an MRI can detect anything wrong).
A PET scan is able to measure vital functions such as blood flow, oxygen use, and blood sugar metabolism. It identifies organs and tissues that aren’t working as they should much earlier than a CT scan can find these issues.
The whole PET scan process usually takes 2 hours to complete, longer than a CT scan. Part of that time is waiting for your body to absorb the radiotracer.
How Do CT Scans Work?
Specifically, they use a narrow X-ray beam that circles around one part of your body. This provides a series of images from many angles. A computer uses this information to create a cross-sectional picture. Like one piece in a loaf of bread, this two-dimensional (2D) scan shows a “slice” of the inside of your body.
This process is repeated to produce a number of slices. The computer stacks these scans one on top of the other to create a detailed image of your organs, bones, or blood vessels. For example, a surgeon may use this type of scan to look at all sides of a tumor to prepare for an operation.
How Are CT Scans Done?
You'd probably get a scan at a hospital or radiology clinic. Your doctor might tell you not to eat or drink for a few hours before the procedure. You may also need to wear a hospital gown and remove any metal objects, such as jewelry.
A radiology technologist will perform the CT scan. During the test, you’ll lie on a table inside a large, doughnut-shaped CT machine. As the table slowly moves through the scanner, the X-rays rotate around your body. It’s normal to hear a whirring or buzzing noise. If you move, it can blur the image, so you’ll be asked to stay very still. You may need to hold your breath at times.
How long does a CT scan usually take?
A CT scan usually takes about a half-hour from start to finish. Most of the time is used for prep, but the actual time for the scan itself is short, usually less than 30 minutes. Sometimes it may take longer if you have to drink contrast material and wait for it to take effect. The areas of your body that are being scanned can also affect how long the process will take. In most cases, you’ll go home the same day.
What Does a CT Scan Show?
Doctors order CT scans for a long list of reasons:
- CT scans can find bone and joint problems, like complex bone fractures and tumors.
- If you have a condition like heart disease, emphysema, or liver masses, CT scans can spot it or help doctors see any changes.
- They show internal injuries and bleeding, such as those caused by a car accident.
- They can help find a tumor, blood clot, excess fluid, or infection.
- Doctors use them to guide treatment plans and procedures, such as surgeries and radiation therapy.
Can a CT scan detect cancer?
A CT scan can find certain types of cancer and can also:
- Help find a tumor
- Give information that helps your doctor tell what stage cancer is in
- Find the right area to do a biopsy
- See whether a tumor has come back
- Find out if certain treatments are working
Certain cancers are found more easily with a CT scan. CT colonography, for instance, is a diagnostic tool used to find large colorectal polyps and tumors. Studies also show that CT scans work well at diagnosing lung cancer. CT scans can also find cancer in the bladder, kidneys, ovaries, stomach, and pancreas.
CT Scan Cost
There is no one-size-fits-all price for a CT scan. The cost can range from $300 to $6,750.
A CT scan’s cost depends on several things, including, but not limited to:
- Whether you’re having a CT done with or without contrast
- The part of your body that’s being scanned
- Where you live
- Whether you use an inpatient vs. outpatient facility
- Your health insurance
- Whether the facility is in-network or out-of-network
- Fees related to the technician doing the CT scan and the radiologist interpreting the results
- Whether Medicare is a factor in payment
Inpatient vs. outpatient facility costs
When a CT scan is ordered at an inpatient facility like a hospital, the cost will be higher than if you visit an outpatient facility (a free-standing imaging center). Generally, the cost of running a hospital is more, and some of that overhead is passed down to the patient. A CT scan can cost many times as much at an inpatient facility, compared to an outpatient center.
Cost of a CT scan with insurance
The amount you will pay for your CT scan depends on your insurance plan. You may not have to pay any fees, but many insurance plans ask for a copay upfront.
Contact your health insurance provider and ask whether your plan covers CT scans, if you need approval ahead of time, and which imaging place your plan covers.
Cost of a CT scan without insurance
If you don't have insurance, you will likely have to pay out-of-pocket. It could range from a few hundred dollars to a few thousand. You may want to talk to your doctor about how to reduce the overall cost by considering walk-in clinics, urgent care centers, or imaging centers that are not connected with a hospital. You also might qualify for assistance programs, discounts, or payment plans.
Costs of a CT scan with Medicare
If you’re on Medicare, CT scan coverage will depend on which plan you have: Part A, Part B, or Medicare Advantage.
Part A generally will not cover the cost of a CT scan.
If you’re covered under Medicare Part B, 80% of the cost of a CT scan at an outpatient facility will be covered (so, you'll pay 20%). An outpatient facility is defined as CT scans at doctors’ offices, urgent care centers, health centers, outpatient clinics and labs, and surgical centers. The CT scan must be ordered by a doctor, and the facility must take part in Medicare. If you have a CT scan in a hospital setting, you'll pay a copayment.
If you’re on Medicare Advantage, CT scans are covered, but be careful to check if the facility is in-network or out-of-network. Out-of-network coverage may be more expensive, or there may be no coverage for CT scans at all.
What Is a CT Scan With Contrast?
In a CT scan, dense body parts like bones are easy to see. But soft tissues don’t show up as well. They may look faint in the image. To help them appear clearly, you may need a special dye called a contrast material. It blocks the X-rays and appears white on the scan, highlighting blood vessels, organs, or other structures.
Contrast materials are usually made of iodine or barium sulfate. You might receive these drugs in one or more of three ways:
- Injection: The drugs are injected directly into a vein. This is done to help your blood vessels, urinary tract, liver, or gallbladder stand out in the image.
- Orally: Drinking a liquid with the contrast material can enhance scans of your digestive tract, the pathway of food through your body.
- Enema: If your intestines are being scanned, the contrast material can be put into your rectum.
After the CT scan, you’ll need to drink plenty of fluids to help your kidneys get rid of the contrast material.
Are There Any Risks?
CT scans use X-rays, which produce ionizing radiation. Research shows that this kind of radiation may damage your DNA and lead to cancer. But the risk is very small – your chances of developing a fatal cancer because of a CT scan are about 1 in 2,000.
But radiation’s effects add up over your lifetime. So your risk increases with every CT scan you get. Talk to your doctor about the procedure’s potential dangers and benefits, and ask why the CT scan is necessary.
Ionizing radiation may be more harmful in children. That’s because they’re still growing. They also have more years to get exposed to radiation. Before the procedure, you may want to ask the doctor or technician if the CT machine’s settings have been adjusted for a child.
Tell your doctor if you’re pregnant. If you need imaging for your stomach area, your doctor may recommend an exam that doesn’t use radiation, such as an ultrasound.
CT Scan Side Effects
Some people are allergic to the contrast materials. Most of the time, the reaction is mild. It can lead to itchiness or a rash. In very few cases, the dye may trigger a life-threatening reaction. For this reason, your health care provider may want to monitor you for a short period after your CT scan. Tell your doctor about any allergies you have to medications, seafood, or iodine.
Your doctor should know, too, if you have diabetes and are taking the drug metformin. They’ll let you know if you should stop taking your medication before or after your procedure.
Although it’s rare, contrast materials can lead to kidney problems. Let your doctor know if you have any kidney issues before the CT scan.
A CT scan is an imaging test that uses X-rays and a computer to create pictures of your organs, bones, and other tissues. Depending on what body part is being scanned, you might have to drink what's called a contrast material to make softer tissues show up better in the imaging.
CT scans can help your doctor diagnose a variety of conditions, including cancer.
Because CT scans use X-rays, there is some risk involved, and you may have some side effects.
CT Scan FAQs
- What’s the liquid you drink before a CT scan?
You may need to drink barium sulfate, a contrast agent that will help highlight your internal organs and other tissues. The liquid helps make specific tissues, organs, and blood vessels easier to see. The contrast material usually leaves your system in 24 hours.
- Why do you have to fast before a CT scan?
You will need to watch what you eat and drink at least 4 hours before your CT scan. Drinking only clear liquids will help prevent nausea that may happen from drinking the contrast material. You can have tea, black coffee, broth, or gelatin.
- How long do you have to wait for the results of a CT scan?
It usually takes 24-48 hours to get results from a CT scan. A radiologist will read, interpret, and report the findings.
- Can you feel sick after a CT scan with contrast?
It is rare to have an allergic reaction or medical problems with CT scan contrast. Most reactions are mild and cause itchiness or a rash. In rare situations, the contrast could potentially cause a serious and life-threatening reaction. Let your doctor know if you’ve had reactions to contrast in the past.
You could have nausea and vomiting after you drink the contrast material. Some people have headaches and dizziness.