According to some aspects, an x-ray apparatus for imaging and/or radiation therapy is provided, the x-ray apparatus comprises an electron source capable of generating electrons, at least one first target arranged to receive electrons from the electron source, the at least one first target comprising material that, in response to being irradiated by the electrons, emits broad spectrum x-ray radiation, at least one second target arranged to receive at least some of the broad spectrum x-ray radiation, the at least one second target comprising material that, in response to irradiation by broad spectrum x-ray radiation from the first target, emits monochromatic x-ray radiation, and at least one detector positioned to detect at least some of to the monochromatic x-ray radiation emitted from the at least one second target. According to some aspects, a relatively low cost, relatively small footprint x-ray apparatus for generating monochromatic x-ray radiation suitable for medical/clinical purposes and appropriate for use in existing medical facilities such as hospitals and/or small clinical settings is provided.