Method and arrangement for controlling an X-ray beam

An X-ray system comprising:

• at least one X-ray tube;
• at least one X-ray detector that is movable relative to said at least one X-ray tube;
• a position determination system for automatically electronically obtaining position data identifying a position of at least one of an X-ray tube designated for an examination and an X-ray detector designated for said examination, before activating said designated X-ray tube to emit X-rays in said examination;
• a position correlation unit for, using said position data, automatically electronically determining respective positions of said designated X-ray tube and said designated X-ray detector relative to each other, and for comparing said relative positions to correct relative positions for said examination;
• and
• an activation unit which checks whether said designated X-ray detector is activated and which allows activation of said designated X-ray tube to emit X-rays in said examination only if said designated X-ray detector is activated and said designated X-ray tube and said designated X-ray detector are in said correct relative positions.