Hospitals generally require an x-ray of the chest, but feel free to refuse this if you have come in for hospitalization for a
broken foot, for example. While one should not fear taking an
x-
ray for any reasonable purpose, there is no "safe" threshold for radiation exposure. Do not have an x-ray taken by a chiropractor. The x-ray machines in these offices are usually purxchased second-hand and are out of calibration, which means they provide more radiation than is necessary.