A chest CT scan performed to evaluate COVID-19 or its aftermath typically exposes a patient to **about 4 to 6 millisieverts (mSv) of radiation**. This amount varies depending on whether contrast dye is used; a non-contrast chest CT usually delivers around 4 mSv, while a contrast-enhanced scan can increase exposure to approximately 6 mSv. For comparison, the average person receives about 3 mSv of natural background radiation annually, so a chest CT scan represents roughly one to two years’ worth of natural radiation exposure.
To put this into perspective, a standard chest X-ray emits about 0.1 mSv, which is much lower than a CT scan. The higher radiation dose in CT scans is due to the detailed cross-sectional images they produce, which require multiple X-ray exposures from different angles. This detailed imaging is crucial for assessing lung abnormalities caused by COVID-19, such as ground-glass opacities, fibrosis, or other residual lung damage that may persist after infection.
The use of chest CT scans during the COVID-19 pandemic has been important for diagnosing and monitoring lung involvement, especially in patients with moderate to severe disease or those with persistent respiratory symptoms months after infection. However, because CT scans involve ionizing radiation, medical guidelines recommend using them judiciously—primarily when the clinical benefits outweigh the risks of radiation exposure.
Radiation exposure from a single chest CT scan is generally considered safe for most patients, but repeated scans should be carefully considered to avoid cumulative radiation risks. The risk from a single CT scan is low, but it is not zero, and minimizing unnecessary imaging is a standard practice in radiology.
In summary, a chest CT scan for COVID-19 typically involves radiation exposure in the range of 4 to 6 mSv, which is significantly higher than a chest X-ray but still within a range considered acceptable for diagnostic purposes when clinically indicated. The decision to perform a CT scan balances the need for detailed lung imaging against the potential risks of radiation exposure.
