An x-ray detector assembly includes a curvilinear detector assembly that has a first side section that includes a first plurality of detector modules, a second side section that includes a second plurality of detector modules, and a third section that includes a third plurality of detector modules. The third section is positioned between the first and second side sections in a channel direction. The x-ray detector assembly also includes a first flat panel digital projection detector and a first detector mounting structure that is configured to align the first flat panel digital projection detector in a first position to block the third section of the curvilinear detector assembly from receiving x-rays emitting from an x-ray source toward the curvilinear detector assembly in the x-ray penetration direction.