A variable aperture assembly for an imaging system having a radiation detector housing,comprising: a base ring having a first opening; a plate having a first aperture and adapted to engage the base ring such that the first aperture is disposed over the first opening; at least one aperture blade each operatively coupled to the base ring so that the at least one aperture blade is adapted to move laterally relative to the first aperture, wherein the at least one aperture blade includes a second aperture formed therein, wherein the at least one aperture blade includes a first aperture blade comprising: a first end rotatably coupled at a pivot point to one of the base ring or the plate; a second end adapted to be pivoted relative to the first end; and an inner portion disposed between the first and second ends, the inner portion defining the second aperture; and an aperture drive mechanism having a body and an actuator coupling member extending at an angle from the body, the body being operatively coupled to the base ring and to each aperture blade such that the aperture drive mechanism drives each aperture blade laterally away from the first aperture in response to the actuator coupling member being moved in a first lateral direction, and laterally over the first aperture such that the second aperture is disposed over the first opening in response to the actuator coupling member being moved in a second lateral direction. a base ring having a first opening; a plate having a first aperture and adapted to engage the base ring such that the first aperture is disposed over the first opening; at least one aperture blade each operatively coupled to the base ring so that the at least one aperture blade is adapted to move laterally relative to the first aperture, wherein the at least one aperture blade includes a second aperture formed therein, wherein the at least one aperture blade includes a first aperture blade comprising: a first end rotatably coupled at a pivot point to one of the base ring or the plate; a second end adapted to be pivoted relative to the first end; and an inner portion disposed between the first and second ends, the inner portion defining the second aperture; and an aperture drive mechanism having a body and an actuator coupling member extending at an angle from the body, the body being operatively coupled to the base ring and to each aperture blade such that the aperture drive mechanism drives each aperture blade laterally away from the first aperture in response to the actuator coupling member being moved in a first lateral direction, and laterally over the first aperture such that the second aperture is disposed over the first opening in response to the actuator coupling member being moved in a second lateral direction. a first end rotatably coupled at a pivot point to one of the base ring or the plate; a second end adapted to be pivoted relative to the first end; and an inner portion disposed between the first and second ends, the inner portion defining the second aperture; and an aperture drive mechanism having a body and an actuator coupling member extending at an angle from the body, the body being operatively coupled to the base ring and to each aperture blade such that the aperture drive mechanism drives each aperture blade laterally away from the first aperture in response to the actuator coupling member being moved in a first lateral direction, and laterally over the first aperture such that the second aperture is disposed over the first opening in response to the actuator coupling member being moved in a second lateral direction.