Modern medicine offers a variety of diagnostic methods and tools that include imaging techniques where patients are exposed to ionizing radiation such as X-radiography, CT scans, PET and others. In many countries, for example, the use of CT scans has continuously increased representing today an indispensable tool in X-ray diagnostics (UNSCEAR 2010). As a result, in particular in developed countries with health-care level I, even if averaged over the whole population of a certain country, medical exposures are largely responsible for exposure from manmade sources of ionizing radiation (UNSCEAR 2010). Recent studies suggest cumulative effective doses of more than 100 mSv from CT scans * W. Rühm