Patent ID: 7630477

Claim:
A computed tomography (CT) system comprising: a rotatable gantry having an opening to receive a subject to be scanned in a subject area; a high frequency electromagnetic energy projection source configured to project a high frequency electromagnetic energy beam toward the subject area; a pre-subject filter assembly including: a pair of filters, each filter defined by a base, tail, and curved portion connecting the base to the tail, and wherein the pair of filters are arranged such that the curved portion of one filter generally faces the high frequency electromagnetic energy projection source and the curved portion of another filter generally faces the high frequency electromagnetic energy projection source, wherein the filters are separately moveable along a plane at a right angle to a central beam of x-rays emitting from the high frequency electromagnetic energy projection source; and a third filter having a length perpendicular to the central beam of x-rays, the length being longer than at least one of the first and second filters.