From the Guidelines
The radiation dose of a CT scan can be as low as 0.5 mSv, which is equivalent to 2 months of background radiation in the USA, when using optimal techniques and lowest possible radiation dose that still results in appropriate quality images. The radiation dose of a CT scan typically ranges from 1-10 millisieverts (mSv) per scan, though this varies significantly based on the body part being examined and the specific protocol used [ 1 ]. For example, abdominal CT scans expose a patient to an effective radiation dose of approximately 10 mSv [ 1 ], while chest CT scans can deliver about 7 mSv. However, with the use of optimal techniques, such as suspending the automatic exposure control function on the CT scanner and applying a specific tube voltage and current according to patient size, the radiation dose can be significantly reduced [ 1 ].
Key Considerations
- The benefit of accurate diagnosis typically outweighs the small risk of radiation exposure for most patients [ 1 ].
- Healthcare providers follow the ALARA principle (As Low As Reasonably Achievable) when ordering imaging studies, and newer CT technologies continue to reduce radiation doses while maintaining image quality [ 1 ].
- Patients should inform their doctors about previous radiation exposures and discuss whether alternative imaging methods like MRI or ultrasound might be appropriate for their specific situation.
- The overall dose of a CT scan can vary depending on the CT scanner and patient size, but using optimal techniques can result in a dose as low as 0.5 mSv [ 1 ].
Reducing Radiation Dose
- Strategies to reduce the radiation dose include suspending the automatic exposure control function on the CT scanner and applying a specific tube voltage and current according to patient size [ 1 ].
- Using a low radiation dose, approximately one third of that required for the inspiratory film, can detect air trapping on the expiratory film [ 1 ].
From the Research
Radiation Dose of CT Scan
- The radiation dose of a CT scan can vary significantly depending on the type of scan and the patient's age and sex 2
- A study found that the median effective doses of CT scans ranged from 2 millisieverts (mSv) for a routine head CT scan to 31 mSv for a multiphase abdomen and pelvis CT scan 2
- The estimated lifetime attributable risk of cancer from a CT scan also varies widely, with an estimated 1 in 270 women who underwent CT coronary angiography at age 40 years developing cancer from that CT scan, compared to an estimated 1 in 8100 women who had a routine head CT scan at the same age 2
- A more recent study projected that approximately 103,000 future cancers over the course of the lifetime of exposed patients could result from CT examinations in 2023, with the most common cancers being lung, colon, leukemia, and bladder cancer 3
Factors Affecting Radiation Dose
- The radiation dose of a CT scan can be affected by several factors, including detector configuration, tube current, tube potential, reconstruction algorithm, patient positioning, scan range, reconstructed slice thickness, and pitch 4
- Manipulating these factors can help reduce the radiation dose while preserving diagnostic image quality 4
Comparison with Other Imaging Modalities
- CT scans are often compared to other imaging modalities, such as magnetic resonance angiography (MRA) and ultrasound, which have different advantages and disadvantages in terms of radiation exposure, cost, and image resolution 5, 6
- For example, MRA provides a noninvasive option with no radiation exposure, but its high cost and limited availability restrict its widespread clinical use 5