A radiation therapy apparatus includes a housing, a radiation source carried by the housing, and an aperture assembly carried by the housing. The aperture assembly includes a radiation aperture body, an aperture holder and a cover. The radiation aperture body has a shaped opening therein to control a radiation dosing profile. The aperture holder has an aperture-receiving passageway therein receiving the radiation aperture body, and a recessed end. The cover is received within the recessed end of the aperture holder, and retains the radiation aperture body within the aperture holder. The cover has an opening aligned with the shaped opening in the radiation aperture body. A radiation filter is carried by the housing.
