What is a CAT Scan?
A CAT scan, also known as computed tomography (CT) scan, is a medical imaging technique that uses X-rays and computers to create cross-sectional images of the body (WebMD, 2023). The “CAT” in CAT scan stands for “computed axial tomography”, referring to the process of combining multiple X-ray images taken from different angles to produce cross-sectional views (Cleveland Clinic, 2023).
During a CAT scan, the patient lies on a table that moves through a large donut-shaped machine. Multiple X-ray beams are aimed at the body from all angles as the table moves through the machine. Detectors on the opposite side of the machine record the X-rays that pass through the body. The X-ray images are fed into a computer, which processes them to create cross-sectional views or “slices” of the internal organs and tissues (WebMD, 2023).
CAT scans are commonly used to diagnose diseases and injuries as they provide clear and detailed images of the internal structures of the body. They can detect tumors, infections, organ damage, bleeding, fractures, and more. Doctors often use CAT scans of the head, chest, abdomen, pelvis, and spine to help diagnose conditions and guide medical treatment.
Sources:
https://www.webmd.com/cancer/what-is-a-ct-scan
https://my.clevelandclinic.org/health/diagnostics/4808-ct-computed-tomography-scan
Potential Cancer Risks
CAT scans, also known as CT scans, use ionizing radiation to generate images of the inside of the body. Ionizing radiation has enough energy to damage DNA and potentially cause cancer (source). The level of radiation exposure from a single CAT scan is fairly low, ranging from 1 to 10 mSv. To put this in perspective, the average person is exposed to 3 mSv of background radiation annually (source). However, exposure is cumulative. Multiple CAT scans or scans done at a younger age can increase lifetime cancer risk.
The radiation exposure from a single chest X-ray is about 0.1 mSv, so a CAT scan exposes patients to much more radiation than a typical X-ray (source). Still, the potential risk from any single medically necessary CAT scan is very small, especially compared to the diagnostic benefits.
Factors That Increase Risk
One of the main concerns with CT scans is the increased radiation exposure for patients. While a single scan may not pose significant risk, the cumulative effects of multiple scans over time can increase cancer risk. There are several factors that can heighten this risk:
Cumulative radiation exposure is a major factor. Patients who undergo multiple CT scans over months or years accumulate higher doses of radiation.[1] Studies show increased cancer rates in patients who have had 5 or more scans.[2] It’s important for doctors and patients to consider the patient’s scan history and weigh the benefits vs potential risks.
Children and pregnant women are more sensitive to radiation. Children have longer lifespans ahead during which cancer could potentially develop. The rapidly dividing cells of a developing fetus are also more susceptible to radiation damage.[3] Extra precautions should be taken when scanning these populations.
Errors in CT scanner calibration can deliver higher than expected doses. Quality control and technician training help minimize these risks.[2] Patients can ask their imaging center about quality assurance programs to ensure proper scanner function and safety protocols.
Ways to Reduce Risk
While CT scans involve some radiation exposure, there are steps patients and providers can take to minimize potential risks:
Limit scans when possible. Patients should discuss with their doctor whether a CT scan is truly needed or if alternative tests may suffice. Scans should only be done when there is a clear medical benefit that outweighs the small radiation risk.
Use alternative tests when practical. In many cases, an ultrasound, MRI or low-dose x-ray may provide the needed diagnostic information without ionizing radiation. Patients should ask their doctor about alternatives that avoid CT exposure.
Follow safety protocols on machine use and maintenance. CT scanners should be properly calibrated and maintained to ensure radiation doses are as low as possible while still producing a useful image. Technicians must follow protocols to use the minimum exposure needed.
References:
https://www.fda.gov/radiation-emitting-products/medical-x-ray-imaging/what-are-radiation-risks-ct
https://www.health.harvard.edu/cancer/radiation-risk-from-medical-imaging
Interpreting the Risk
While CT scans do expose patients to a small amount of radiation, the potential increased cancer risk is quite low, especially compared to the benefits of accurately diagnosing medical conditions. According to the FDA, the increased risk of developing a fatal cancer from a 10 mSv CT scan is estimated to be 1 in 2000. This is an extremely small increase in risk that needs to be put into proper context (FDA).
For many patients, the substantial benefits of CT scans in detecting tumors, heart disease, internal injuries and other conditions far outweigh the small potential increase in cancer risk. Early detection and diagnosis of medical conditions through CT scans often leads to more successful treatment and better health outcomes. Researchers have found the benefits of appropriate CT screening in detecting issues early on can prolong productive life expectancy (Harvard Health).
It’s important for patients to have an informed discussion with their doctor about the potential benefits and risks of CT scans for their specific health situation. In many cases, a CT scan is the most effective diagnostic tool with a small radiation trade-off that is well worth gaining more information to make the right medical decisions and catch issues early on if present.
Scan Procedure Safety
CT scans use X-rays to take multiple images of the body from different angles. The scanner itself is a large donut-shaped machine that has a motorized table you lie down on that moves slowly through the center opening during the scan. You may hear buzzing or clicking noises during the procedure as the internal parts of the machine rotate around you. Here are some of the main precautions taken during the scan to limit radiation exposure:
The technologist will position you on the scanner table and may use pillows or other positioning devices to help you hold still during the scan. It’s important not to move during the imaging process so the pictures come out clear.
You may be asked to remove any metal objects like jewelry beforehand since these can interfere with image quality. The technologist may also give you a gown or scrubs to change into.
Lead shielding is built into the scanner machine itself to help block scattered radiation. This can include movable lead shields that can be positioned over sensitive areas like the eyes or genitals to limit exposure.
The scanner is operated from a separate control room so the technologist is not exposed to radiation while running the machine. They can see you through a window and can hear you via intercom if you need assistance.
The amount of radiation is precisely controlled by the scanner software and is tailored to your body size. Modern scanners can modulate the dose so that you receive the minimum amount needed for high quality images.
By following safety protocols and using shielding, the amount of radiation exposure from a medically necessary CT scan is very low. Your radiologist and technologist work to get the images needed while limiting radiation as much as possible.
After the Scan
Once the CT scan is complete, there is no radiation remaining in your body. The scanning device only emits radiation during the imaging process. According to the Mayo Clinic, “After the exam you can return to your normal routine.” 1
After the scan, the images are reviewed by a radiologist, a physician who specializes in medical imaging. The radiologist will analyze the images from the scan and send a report to your doctor. Your doctor will then review the radiology report, along with your medical history and any other tests, to make a diagnosis and recommend treatment if needed. So while the scan itself may only take 10-30 minutes, the full process includes image analysis by specialists before your doctor can interpret the results.
Signs of Potential Issues
A CAT scan itself does not cause any immediate symptoms or health effects. The radiation exposure from a single CAT scan is relatively low, so you likely won’t experience any signs of radiation sickness like nausea or fatigue right after the test (1).
However, the radiation exposure does carry a small potential long-term cancer risk. But because cancer can take years or decades to develop, it’s very difficult to directly attribute a cancer later in life to a specific CAT scan done years earlier. According to the FDA, “Because of the small potential risk…and the fact that it’s cumulative over a lifetime, the decision whether to have a CT scan during pregnancy should be based on careful consideration of the justification for the CT scan and consultations between the referring physician, the radiologist and the patient” (2).
So while a single CAT scan is unlikely to cause immediate health issues, the potential long-term cancer risks should be considered, especially with repeated or excessive CAT scan exposure over time.
Sources:
(1) https://www.mayoclinic.org/diseases-conditions/radiation-sickness/symptoms-causes/syc-20377058
(2) https://www.fda.gov/radiation-emitting-products/medical-x-ray-imaging/what-are-radiation-risks-ct
Better Decision Making
When your doctor recommends getting a CT scan, it’s important to have an open discussion about whether it’s truly necessary or if other imaging alternatives may be sufficient. Although CT scans provide valuable diagnostic information, the radiation exposure is not insignificant. Those at higher risk may want to be especially cautious.
Discuss with your doctor if your specific symptoms can be adequately evaluated with an ultrasound, MRI or other imaging method. While CT scans are ideal for detecting issues in bone and detecting some cancers, alternatives like MRI provide tremendous soft tissue detail without radiation. Ultrasound is often sufficient for initial evaluation of abdominal issues.
Understand your own risk factors, like a family history of cancer, previous radiation exposure, or if you are a child or pregnant woman. Share these with your physician to enable the best scan decision. While doctors strive to order scans judiciously, more information allows them to make the most informed choice.
Ask if another type of scan is reasonable for your situation. While CT is preferred for many uses, each case differs. Discuss alternatives to enable shared decision making. Although some situations clearly warrant CT, many gray areas exist where another modality may be reasonable if radiation is a substantial concern.
The Bottom Line
CAT scans involve some radiation risk. This risk is small, but should be considered. The amount of radiation in a single CT scan is fairly small and the risk of developing cancer from it is low, especially compared to the benefits of accurate diagnosis and treatment planning. However, multiple CT scans over time can increase cancer risk, especially in children whose tissues are more sensitive.1
Talk to your doctor about the need for scans and reducing any unnecessary exposure. Make sure the benefits outweigh the small risks. Doctors can help determine if alternative tests are available, minimize scan areas, or space out scans over time to reduce exposure when possible. Knowing the risks allows patients to make more informed decisions.2
