A system for the inspection of the internal structure of a target includes at least one x-ray source that emits collimated x-rays to irradiate the target. At least one detector is positioned to detect backscatter x-rays from the target. The detector may include a collimation slot that limits the field of view of the detector. The target may be a railway component and the system may inspect the internal structure of the component as it is moved along the railway by a vehicle. The system may detect a change in the density of a target based on a comparison of the detected backscatter x-rays. The use of a plurality of segmented backscatter x-ray detectors having a collimation slot may pixelate the internal image in the direction of the collimation slot.