You may have seen headlines recently about a link between CT (computed tomography) scans and cancer due to radiation exposure. CT scans project X-rays into the body to produce detailed images and are often necessary in situations where a medical diagnosis needs to be made quickly. While they are generally considered safe, multiple CT scans over time pose a small increase in cancer risk.
To keep you safe, radiologists take steps to reduce your exposure as much as possible.
Bradley Delman, MD, MS
In this Q&A, Bradley Delman, MD, MS, a neuroradiologist and Vice Chair of Quality at Mount Sinai, explains the benefits of CT scans and how radiologists work to reduce the risks.
What is a CT scan, and why is it important for diagnosing health conditions?
CT is a powerful tool that uses carefully focused beams of radiation to generate images inside the body. These scans enable doctors to see structures in three dimensions to diagnose a wide variety of conditions including strokes, bleeding, infections, tumors, and traumatic injuries. Sometimes dye is injected into the veins to improve visualization of blood vessels, tumors, and inflammation. These scans have become invaluable for emergency situations and presurgical planning.
Can CT scans increase my risk of developing cancer from radiation exposure?
CT machines do expose patients to ionizing radiation, which over time can damage DNA. Fortunately, DNA is believed to repair itself in most instances. DNA that does not get repaired can slightly increase your long-term risk for cancer. Cumulative exposure from multiple CT scans over time may cause DNA damage to accumulate, and that is also believed to increase cancer risk.
It’s important to note that we only scan when necessary and that we use the lowest radiation doses necessary for diagnosis. Scanners are getting even more efficient at this. Ultimately, we must compare the risks and the benefits, and it is more essential to diagnose and treat what is wrong with the patient now than to be concerned with the very low potential for cancer years into the future. Our scanners use low radiation doses overall, so the risk is thought to be justified by the value scans provide in patients’ care.
Benefits:
- Fast, accurate diagnosis with detailed images
- Ideal for emergencies and presurgical planning
Risks:
- A small risk for radiation-induced DNA damage
- Small potential for increased risk of cancer with multiple scans over time
- Potential allergic reaction to the contrast dye (if used)
What are the safest alternatives to CT scans for medical imaging?
Low- or no-radiation alternatives to CT scans include X-rays, ultrasounds, and magnetic resonance imaging (MRIs). These do have their role and are used when they can provide comparable or superior information, but CT is fast and reliable, and has become an essential part of diagnosis, especially in the Emergency Department.
How does the number of CT scans I get affect my long-term cancer risk?
If you have many CT scans over a short period, the long-term risk for cancer is thought to be higher than with fewer scans, or with scans spaced apart. But again, we should be concerned about diagnosis and treatment of the ill patient. Scans are offered only when they offer clinical value.
How do radiologists minimize radiation dose from CT scans while ensuring accurate results?
Our responsibility is to keep doses as low as we can. To do that, we follow the “As Low As Reasonably Achievable,” or ALARA, principle:
- Using low-dose CT scan protocols
- Scanning only your necessary body parts
- Limiting the scan coverage to what is necessary
- Basing scan settings on your age, weight, and scan type
- Optimizing protocols from the companies that build our advanced CT scanners, which require less radiation than older models
How is my radiation exposure from multiple CT scans tracked to reduce long-term health risks?
Many hospital systems, including Mount Sinai, use digital imaging records and dose tracking systems to monitor patient exposures. We continually use radiation exposure data to refine and optimize our scanning protocols. This tracking does not mitigate radiation risks for individual patients, but it does create transparency for patients to understand their doses over time.