[Radiation dose in computed tomography. Risks and challenges].

The exponentially growing performance of newer scanner generations has increased diagnostic opportunities and utilization of computed tomography. The excellent clinical results with CT, however, have to be weighed against a high radiation exposure. While radiation exposure with modern scanners is well below the diagnostic reference values of the EU for most organ systems, radiation dose for retrospectively gated cardiac examinations can be substantially higher: organ doses can reach 100 mGy, a dose for which cancer induction been proven. For children, the situation may also be critical if scanning parameters are not adapted to their smaller size and increased radiation risk: the risk-benefit ratio may then no longer favor CT. The application of CT for young patients, patients with favorable prognosis and for frequent follow-up examinations will increase the radiation risk to the individual and the population. The growth rates for CT utilization in Germany are well below those in the United States but the increasing number of exams will lead to a substantial increase in population dose even if the dose per individual exam can be reduced. The combination of optimum scanning parameters, automated dose modulation and dose adaptation to the individual patient will help contain radiation dose. Further reduction is possible by reducing the number of scan phases, limiting the scan length and choosing a lower tube voltage. Most important, however, is the close collaboration with referring physicians: scanning technique and choice of imaging modality can only be adapted if the clinical question is clearly defined. In the light of radiation exposure the critical and knowledgeable use of CT becomes the more important the easier it is to request an exam and the better the clinical results.