DIGITAL BEAM ATTENUATOR FOR DSA AND CHEST RADIOGRAPHY.
During the past year our group has investigated an extension of the concept of beam compensating filters. Our approach involves the acquisition of a low dose patient positioning image which is digitized and used to drive a mechanism which places attenuating materials in the x-ray beam. Our initial experiments involved a 6 multiplied by 6 array of pistons which deformed a bladder filled with cerous chloride. This device had inadequate spatial resolution and excessive common mode x-ray attenuation. More recently we have developed a technique involving a digitally controlled dot-matrix printer equipped with a ribbon containing cerium oxide. This is used to type an attenuating image of the patient. This attenuator is then servoed into the x-ray beam. Current attenuator formation times are on the order of five minutes. Soon we hope to be able to accomplish this in 30 seconds. Preliminary results using a Humanoid chest phantom and laboratory animals demonstrate the distinct advantages of the technique. Image quality relative to uncompensated images is striking in simulated chest radiography and DSA.
