Patent Number: 
Section: claims

1. A radiographic imaging system comprising:a scanning bay;a movable table configured to move a subject to be scanned fore and aft along a first direction within the scanning bay;an x-ray projection source configured to project x-rays in an x-ray beam toward the subject;a pair of generally cylindrically-shaped rotatable filters formed of attenuating matter, each filter rotatable about a line of rotation that extends along a long axis of the filter and is defined to be transverse to the x-ray beam; anda computer programmed to:determine a region-of-interest of the subject; androtate at least one rotatable filter of the pair of rotatable filters such that the pair of rotatable filters limit x-ray exposure outside the region-of-interest. 2. The radiographic imaging system of claim 1 wherein each cam filter has a length and an attenuation profile that varies as a function of filter length. 3. The radiographic imaging system of claim 1 wherein an attenuation profile of each filter is a function of filter thickness. 4. A cam filter assembly for use with a radiation emitting imaging system, the cam filter assembly including a pair of non-overlapping cam filters wherein each cam filter has a generally rod-shaped body and has an attenuation power that varies with thickness of the filter, the pair of cam filters being configured to be independently rotated to collectively manipulate a beam of radiation projected toward a subject to generate a desired radiation profile across a region-of-interest of the subject. 5. The cam filter assembly of claim 4 wherein each filter has a width situated along an x-axis and a length situated along a z-axis, the z-axis being parallel to a long axis of the subject, and wherein each filter has varying attenuation characteristics along its length.