A controller and a related method of controlling a collimator. The controller operates to select a collimator setting for collimator of an x-ray imager for acquiring an image of a ROI in a patient. The controller operates to select the collimator setting to optimize the patient dosage in respect of primary radiation and secondary radiation dosage of medical staff. A position detector supplies to the controller a current position of a person relative to a patient. Based on said supplied position, the controller's configured to perform an optimization procedure that takes into account the staff dosage in respect of the secondary radiation dosage to reduce the secondary radiation dosage.