X-ray portal imaging detectors have multiple layers, such as multiple layers of phosphor screens and/or detectors. Some x-rays that pass through one layer are detected or converted into light energies in a different layer. For example, one phosphor screen is provided in front and another behind that panel detector circuitry. Light generated in each of the phosphor screens is detected by the same detector circuitry. As another example, multiple layers of phosphor screens and associated detector circuits are provided. Some x-rays passing through one layer may be detected in a different layer. High energy x-rays associated with Megavoltage sources as well as lower or higher energy x-rays may be detected.