Is radiation exposition actually harmful?
There are studies showing that low doses of radioactivity are healthy (Hormesis). Considering roundworms, it is proven that they can live longer, after radiation exposure. Nonetheless, there are no scientific studies proving that low doses really are harmful (L.E. Feinendegen: Biologic Responses to Low Doses of Ionizing Radiation Detriment Versus Hormesis Part I+II. Journal of Nuclear Medicine 2001). Under a low dose is considered to be lower than 285 mSV.
The dose during a PET/CT examination is added up to merely 14 mSV. Feinendegen actually says that the hypothesis of radioactive radiation being carcinogenic even at low doses, is simply unfunded and wrong (L.E. Feinendegen: Evidence for beneficial low level radiation effects and radiation hormesis. British Journal of Radiology 78-2005). Radiation protection laws in Germany assume a linear dose-effect relationship without threshholddose.