It’s normal to feel a little anxious before getting any medical test or procedure. A CT or CAT scan uses X-rays and computers to take detailed pictures inside your body, which can sound intimidating. However, there are many reasons why a CT scan is not something to worry about too much.
What exactly is a CT scan?
A CT or CAT scan (computed axial tomography) is a diagnostic imaging test that uses X-rays and computers to create detailed cross-sectional pictures inside your body. The “slices” taken by the CT scanner can be combined by a computer to produce 3D images that visualize structures inside the body in great detail. CT scans are performed at hospitals and imaging centers by trained technologists.
During the test, you will lie on a table that slides into a large, tunnel-like scanner. The scanner consists of an X-ray tube that rotates around your body and produces narrow beams of radiation. Detectors on the opposite side of your body then pick up the signals and send the information to a computer, which assembles these signals into images of slices or cross-sections of the area being examined.
The actual scan typically takes only 10 to 30 minutes, depending on which part of the body is being imaged. The entire process, including prep time, takes about an hour.
Why do doctors order CT scans?
CT scans are used to examine almost all parts of the body and are commonly performed to:
- Get more detailed information than regular X-rays
- Diagnose causes of symptoms like pain, swelling or infection
- Detect tumors, cysts, blood clots, bleeding or other abnormalities
- Pinpoint the location of a tumor before biopsy or surgery
- Examine injuries to the chest, abdomen, spine, neck or head
- Look at blood vessels, bones and organs like the heart, liver and kidneys
- Identify conditions like appendicitis, cancer, heart disease and pulmonary embolism
- Detect fractures or other bone abnormalities
- Plan radiation therapy for cancer
- Guide procedures like needle biopsies and tumor ablations
- Monitor the effectiveness of certain treatments
Some common reasons for a CT scan include unexplained pain, bleeding or symptoms of cancer. CT scans are often used in emergency cases like trauma or suspected internal injuries. They are a quick, noninvasive way for doctors to get a clear look inside your body.
Are CT scans safe?
CT scans involve a small amount of radiation exposure. The amount of radiation is considered safe for most people as long as the scan is medically justified. However, unnecessary or repeat CT scans should be avoided.
The benefits of a medically necessary CT scan almost always outweigh the risks from radiation. Doctors do not order CT scans if they do not think it is the best test for your specific medical needs. Steps are taken to limit radiation exposure as much as possible, especially for children and pregnant women.
Each CT scan uses about the same radiation dose as 100 to 200 X-rays. The doses vary based on the type of CT scan. The average person in the US gets exposed to a small amount of radiation yearly from natural sources and medical tests, so most doctors agree that CT scans are a worthwhile risk overall.
Radiation risk factors
Some people have a higher risk of potential harm from the radiation exposure of CT scans:
- Children and unborn babies – Children’s growing bodies are more sensitive to radiation. Though the risk is low, children who get multiple CT scans may have a very small increased lifetime risk of cancer.
- Pregnant women – CT scans of the torso or abdomen expose the fetus to radiation, so these types of CT scans should be avoided during pregnancy if possible.
- Patients who get frequent CT scans – The risks accumulate for those who get CT scans repeatedly over their lifetime.
- Patients with cancers prone to radiation damage – Radiation therapy and CT scans can both raise the risk of second cancers later in some people.
When CT scans are appropriate, the benefits still usually outweigh these small risks. But it is important for doctors to assess each patient individually.
Risk reduction methods
Doctors and technologists take steps to minimize radiation exposure from CT scans when possible:
- Use alternative imaging tests when reasonable – Ultrasound or MRI instead of CT scans for many abdominal or brain issues
- Adjust CT settings based on patient size – Lower radiation settings for smaller patients
- Shield sensitive organs – Lead covers for eyes and breasts
- Focus CT beams – Tightly target scan area
- Child-size protocols – Lower radiation settings for children
Discuss any concerns about radiation with your doctor before agreeing to a CT scan. But keep in mind their medical training helps ensure you only get CT scans when the benefits clearly outweigh the small risks.
How should I prepare for a CT scan?
You typically need little preparation for a routine CT scan. Here are some tips:
- Wear comfortable clothing without metal snaps, zippers or buttons
- Remove jewelry, glasses, hearing aids or other metal objects
- Inform technologist of any implants, devices, drug allergies or health conditions
- Women should tell their doctor if pregnant or breastfeeding
- Fast for about 4 hours before a CT scan with contrast dye
- Arrive early to fill out forms and allow time to get ready
- Ask your doctor if you need specific contrast material
- Follow directions about drinking oral contrast beforehand
- Arrange for someone to drive you home if getting sedation
For some CT scans, you may be given a contrast material called dye before your scan. It can be swallowed, injected through an IV line, or given as an enema. The dye highlights specific areas inside your body, giving clearer details.
If you have any allergies or have reacted to contrast material in the past, make sure your doctor knows before scheduling the CT scan. Certain conditions like asthma, diabetes, dehydration and kidney problems may increase your risks from IV contrast dye and require preparation.
What happens during the CT scan?
When you arrive for your CT scan, a trained technologist will explain the procedure and answer your questions. In the scan room, you will need to remove jewelry or other objects that could affect the images.
For the scan, you will lie still on a table that slides through the round CT scanner opening. The technologist will position you and may strap you in place to prevent movement.
You will hear some buzzing, clicking or whirring noise as the X-ray tube inside the scanner rotates around you. The table may move a bit during the imaging process. Many centers let you communicate with the technologist via intercom during the scan.
It’s important to lie very still during the CT scan to avoid blurring the images. You may be asked to hold your breath for several seconds during the test. The newest CT scanners can produce images very quickly.
An IV contrast dye may be used to enhance visibility of certain tissues. This involves injection of a liquid dye into your vein using a small needle. You may feel warm or flushed afterward. Serious allergic reactions are very rare but can occur.
For a CT scan with oral contrast, you will drink a solution beforehand to highlight areas like your digestive tract. Some patients find the thick liquid unpleasant to drink and experience a temporary coating sensation in the mouth or stomach upset.
After the imaging is complete, the technologist may ask you to wait while they check the images for quality. If needed, they may run the scan again or take additional images.
Does a CT scan hurt?
A standard CT scan is typically painless. You may feel minor discomfort from having to lie still on a hard table. Movement during the scan can cause image blurring and ruin the exam, so the technologist may strap you down firmly.
Some pressure or discomfort may occur when contrast dye is injected through an IV line. This is usually mild and gone once the injection is complete. Oral contrast liquids can sometimes cause mild nausea or diarrhea.
For CT scans of the sinuses or other internal areas, you may feel discomfort or pressure from placement of small tubes or contrast instillation. Let the technologist know if you feel significant pain.
Children and anxious adults may struggle to lie still. Sedation can help keep patients fully immobilized if needed. For young children and babies, a parent may be able to stay and comfort them during the scan.
Overall, CT scanners move quietly and most people can tolerate the brief imaging time without pain medications or sedation. Let your doctor know ahead of time if you are very anxious about enclosed spaces or concerned about pain.
How long does it take to get CT scan results?
The radiologist will analyze your CT images after the scan and send a report to your doctor. This can take a few hours to a few days depending on the urgency of the case.
For medical emergencies, the radiologist prioritizes reading the CT scan right away so those results get back within hours. Outpatient scans may take 1 to 3 days for the full report.
Your doctor will discuss the detailed findings with you at a follow-up appointment. If any concerning findings are seen on the CT scan, your doctor may contact you sooner to discuss next steps.
You can request a CD copy of your actual CT images. However, the scan images need an expert to interpret them – the radiology report explains the findings in a format useful for other doctors.
What do abnormal CT scan results mean?
A radiologist looks over the CT images in sections to identify any abnormal findings. Not all abnormalities are serious or dangerous. Your doctor determines the significance based on factors like your medical history.
Some common abnormal CT scan findings include:
- Masses, cysts or tumors
- Blockages in blood vessels or organs
- Fluid collections or abscesses
- Fractures or bone injuries
- Arthritis or joint damage
- Signs of infection like inflammation
- Bleeding or swollen organs
- Bulging discs or spinal injuries
- Calcification in organs like arteries or kidneys
Your doctor will explain any important findings seen on your CT scan. Additional tests are sometimes needed to make a specific diagnosis and guide treatment. Try not to panic if you hear an abnormal finding – your physician can put the results into context for your health.
Conclusion
While CT scans involve some radiation exposure, this diagnostic test provides detailed views that improve injury diagnosis and disease screening. Using proper precautions, the amount of radiation is considered very low risk compared to the benefits.
Preparing is easy in most cases – just wear comfortable clothes without metal and inform your doctor of any implants or conditions. The test involves lying still for images, sometimes using contrast dye to enhance visibility.
Discomfort is minimal for most patients. Results are analyzed by experts and conveyed to your physician to explain any findings and recommend any needed follow-up. Overall, CT scans are a safe, quick and useful imaging exam. Knowing the simple process can help ease any nerves beforehand.
