X-ray, CT works on the same principle are excited X-rays, in the case of no power on, there is no radiation; in the boot state, there is radiation, and different excitation voltage corresponds to different radiation.
CT radiation is greater than X-ray radiation, X-ray radiation is smaller, checked some of the literature, generally speaking, X-ray radiation is 0.03 mSi - 1 mSi, and CT is 2 mSi - 10 mSi.