From the Guidelines
The maximum acceptable radiation exposure from CT scans per year is 50 millisieverts (mSv) for occupational exposure and 1 mSv for the general public, though there is no absolute limit for medical procedures, and the cumulative effect of multiple scans should be considered, especially for patients requiring repeated imaging, as stated in the 2007 American College of Radiology white paper 1.
Key Considerations
- The benefit of diagnostic information from CT scans typically outweighs radiation risks, and scans are ordered only when medically necessary.
- A single chest CT scan delivers approximately 7 mSv, while an abdominal CT may deliver 10 mSv, which are well below levels known to cause immediate harm.
- Healthcare providers follow the ALARA principle (As Low As Reasonably Achievable) to minimize unnecessary radiation exposure while still obtaining necessary diagnostic information, as also recommended in the 2018 ACC/HRS/NASCI/SCAI/SCCT expert consensus document 1.
Radiation Exposure Limits
- The International Commission on Radiological Protection has reported that CT doses can indeed approach or exceed levels that have been shown to result in an increase in cancer 1.
- The current annual collective dose estimate from medical exposure in the United States has been calculated as roughly equivalent to the total worldwide collective dose generated by the nuclear catastrophe at Chernobyl, highlighting the need for careful management of radiation exposure 1.
Best Practices
- Adoption of and adherence to standardized imaging protocols for standard imaging circumstances is important for consistency and minimizing radiation exposure, as proposed by expert consensus in the 2018 ACC/HRS/NASCI/SCAI/SCCT expert consensus document 1.
- Patient exposure can be minimized by employing best practices and adhering to standardized protocols whenever possible, and ongoing radiation dose monitoring and review are necessary to maintain positive changes in radiation dose reduction 1.
From the Research
Maximum Acceptable Radiation Exposure
- The maximum acceptable radiation exposure per year from CT scans is not explicitly stated in the provided studies, but some studies provide information on the cumulative dose of radiation from CT scans and the associated cancer risk.
- According to 2, exposure to multiple CT scans with a cumulative dose up to 100 mSv (approximately 10 scans), and possibly as high as 200 mSv (approximately 20 scans), does not increase cancer risk.
- However, 3 suggests that cancer risks are positively correlated with radiation dose and CT sites, with an increased risk of cancer associated with higher doses of radiation.
Radiation Exposure Limits
- The studies do not provide a clear maximum acceptable radiation exposure limit per year from CT scans.
- However, 2 mentions that the cumulative dose of radiation from CT scans up to 100 mSv (approximately 10 scans) does not increase cancer risk, implying that this may be a safe limit.
- It is essential to note that the risk of cancer from radiation exposure is still a topic of debate, and more research is needed to determine the safe limits of radiation exposure from CT scans.
Cancer Risk from CT Scans
- 3 found that cancer risks are inordinately increased with CT scans, with an odds ratio of 10.00 (95% CI, 5.87 to 17.05) for lifetime attribution risk.
- However, 2 found that the majority of higher-quality studies (21 out of 25) did not support a causal relationship between low-dose radiation and cancer, suggesting that the risk of cancer from CT scans may be lower than previously thought.
- The discrepancy between these findings highlights the need for further research to determine the true risk of cancer from CT scans.