An X-ray examination apparatus includes an X-ray filter with a plurality of filter elements for locally attenuating the X-ray beam. The X-ray absorptivity of each filter element is controlled by the amount of X-ray absorbing liquid with which the filter element is filled. The filling of ...http://www.google.com.au/patents/US5768340?utm_source=gb-gplus-sharePatent US5768340 - X-ray examination apparatus with x-ray filter
