Conventional radiation doses for CT are on the order of 260 mAs and result in a dose to patients between 5 and 8 millisievert (mSv). Images acquired at 260 mAs are associated with the best contrast and highest spatial resolution, and are aesthetically most pleasing to the eye. With the recent discussion about radiation dose and the movement toward lowering diagnostic doses, one should be cognizant that the lower-dose images have less contrast resolution and become inherently more noisy. This could lead to the inability to correctly detect interstitial disease.
At the highest dose, 260 mAs, there is very nice definition of all the abnormalities. However, dropping the dose on conventional scanners to 100 mAs, less than half the recommended current clinical dose, still appears to allow for detection and accurate characterization of parenchymal disease. Some of the features are lost with 50 mAs, but interestingly, there is good preservation of information as we lower the dose. Therefore, lowering the dose does appear to be possible without losing parenchymal definition.
