A pre-patient collimator for a CT imaging system is provided. The pre-patient collimator includes a collimator housing including a plurality of walls, wherein the plurality of walls includes a first wall configured to face an X-ray source when the pre-patient collimator is coupled to the CT imaging system and a second wall and a third wall flanking the first wall. The pre-patient collimator also includes a bowtie filter assembly disposed within the collimator housing and including a bowtie filter. The pre-patient collimator further includes an adjustment mechanism configured to move the bowtie filter assembly in a lateral direction between the second wall and the third wall within the collimator housing.