From the Guidelines
CT scans use significantly more radiation than initially thought, with doses often 2 to 5 times higher than early estimates suggested, as supported by the most recent study 1 from 2018. Modern CT scans typically deliver between 1 to 14 millisieverts (mSv) per scan, depending on the body part being imaged and the specific protocol used. This is equivalent to approximately 100-700 chest X-rays for a single CT scan. The increased understanding of CT radiation doses came from improved measurement techniques and more comprehensive monitoring, as discussed in the 2007 study by the American College of Radiology 1.
- Key factors influencing radiation dose include:
- Scan length: keeping it to a minimum to encompass only the anatomy of interest
- X-ray beam intensity: determined by both the x-ray tube potential and the x-ray tube current
- Rotation time: exposure increases linearly with rotation time
- X-ray beam filtration: used to selectively attenuate low-energy x-rays
- Scan acquisition mode: different modes can deliver substantially different doses
- The risk of radiation-induced cancer, while small for any individual scan, increases with multiple scans, as highlighted in the 2018 study 1, which notes that approximately 0.4% of all cancers in the United States may be attributable to the radiation from CT studies.
- Healthcare providers now aim to follow the ALARA principle (As Low As Reasonably Achievable) when ordering imaging studies, balancing the diagnostic benefits against radiation risks, especially for children and young adults who are more sensitive to radiation effects and have more years ahead for potential cancer development, as emphasized in the 2018 expert consensus document 1.
From the Research
Radiation Exposure in CT Scans
- The amount of radiation used in a Computed Tomography (CT) scan can vary depending on several factors, including the type of scan and the patient's condition 2.
- A study published in 1993 found that high-resolution CT scans produced significantly less radiation than conventional CT scans, with mean skin radiation doses of 4.4 mGy and 36.3 mGy, respectively 2.
- However, a more recent study published in 2022 found that the cancer risks associated with CT scans were higher than previously thought, with a significant increase in cancer risk observed with increasing radiation dose and multiple CT scan sites 3.
Comparison to Other Imaging Modalities
- CT scans are often compared to other imaging modalities, such as MRI and ultrasound, in terms of their diagnostic accuracy and radiation exposure 4, 5.
- A study published in 2015 found that CT scans were the most accurate method for determining body and carcass composition in livestock, followed by MRI and dual-energy X-ray absorptiometry (DXA) 5.
- However, CT scans typically involve higher radiation doses than other imaging modalities, which can be a concern for patients and healthcare providers 3.
Recent Advances and Future Directions
- Recent advances in nanotechnology have led to the development of new contrast agents and imaging techniques that can help reduce radiation exposure and improve diagnostic accuracy 6.
- Further research is needed to fully understand the risks and benefits of CT scans and to develop new technologies and methods that can minimize radiation exposure while maintaining diagnostic accuracy 6, 3.