A multi-pixel x-ray source is provided. The x-ray source includes a plurality of transmission target assemblies. The transmission target assembly includes a tungsten target and a diamond substrate. The substrate includes a first transmission surface and a second transmission surface opposite first transmission surface. The substrate further includes a first side surface and a second side surface disposed between the first and second transmission surfaces. The target covers the first transmission surface of the substrate. The transmission target assembly further includes a base. The base surrounds the first and second side surfaces of substrate, exposing a collimator surface of the second transmission surface and the target. The transmission target assembly is configured to transmit x-ray generated by the target through the target and the substrate.