Chest x-rays for example dose lots of tissue. CT scans are significantly 100-1000x higher than that and well above whole body average annual radiation exposure. https://en.m.wikipedia.org/wiki/CT_scan
Chest X-rays are a minuscule dose. They are in a similar realm to the dose you get from a long distance flight or 2 - especially if you eat bananas while you fly.
Cardiac CT, chest/abdo/pelvis and PET scans are dose order of magnitude greater though.
