To reduce X-ray exposure, an area of interest is selected in the image. The image of the selected area is updated frequently, comparable to rate of updates used today for the whole image. The rest of the image is updated at a significantly lower rate. Since the area of interest normally is a small part of the overall area, the total exposure is reduced significantly. A movable X-ray shield placed near the X-ray source blocks the radiation from areas outside the area of interest. The shield automatically retracts when the complete image is updated. The area of interest can be selected by the user or automatically selected based on activity in the image.