Cancer screening with CT: dose controversy.

Computed tomographic (CT) cancer screening has seen a steady increase in interest with the introduction of multislice scanners. While the potential benefits of screening are obvious, radiation dose may pose a long-term risk for the screened individual. This article will discuss the basis for radiation risk estimation and give an overview of the current dose controversy surrounding CT screening. Given the current evidence, a non-negligible radiation risk has to be postulated even at very low doses, but estimates depend heavily on the chosen mathematical model. Lung cancer risk is the most important factor in a screening population because it peaks in the time interval between 40 and 70 years of age. Substantial risks for lung cancer development from yearly screening CT examinations are currently discussed in the literature. Risks for colon cancer screening are less because of less frequent screening intervals. For both indications substantial dose reduction up to factors of 5-10 may be possible. Full-body screening remains critical when performed at regular intervals because of the large doses required and the direct exposure of the lungs. If performed in a dose-conscious fashion, individual risks with lung and colon cancer screening are very small, but estimated population risks are non-negligible.