DIGITALLY CONTROLLED X-RAY BEAM ATTENUATION METHOD AND APPARATUS

摘要

DIGITALLY CONTROLLED X-RAY BEAM ATTENUATION METHOD END APPARATUS X-ray compensation masks (51) are prepared by exposing an X-ray target object (43), such as a patient, to a first beam of X-rays. The X-ray fluence from the patient is received by an electronic image receptor (44) which provides an output signal indicating the intensity of the X-rays at all positions in the image field. The image information is converted by an image processor (47) to transformed X-ray intensity values for a plurality of pixels which cover the image field, A mask generating controller (48) determines the minimum transformed intensity value for any pixel, assigns to each pixel an attenuation number which is proportional to the difference between the transformed intensity value for the pixel and the minimum transformed intensity value, and issues control signals to a mask former (49) which deposits on a non-attenuating substrate (50) attenuating masses in a two dimensional array of pixels with the mass thickness in each pixel proportional to the attenuation number. When the mask (51) is inserted into the beam from the X-ray source (41), and a second exposure taken, the X-ray fluency passing through both the attenuating mask (51) and the patient (43) will be substantially equalized across the image field.