How many x-rays exposures/year is the maximum permitted?

For a patient, there is no such limit. As long as it is medically justified to make an x-ray exposure, it should be carried out. The risk of not doing the exam should outdo the risk of radiation hazards. Normally it does. read more

Jan Lidström gives an excellent answer. There is no legal limit, just medical justification. The following is not the way it is done, but to make a comparison. The typical chest x-ray is approximately 5 mrem (to use US units). read more

The radiation exposure from different types of X-ray examination varies widely. An X-Ray of the abdomen uses about 50x as much radiation as a chest X-ray (1 mSv). A CAT scan of the head is about 100 chest X-Rays (2 mSv), and a CT scan of the abdomen + pelvis is about 1000 CXRs (20 mSv). read more