1. An apparatus comprising: an x-ray source for illuminating a part from a plurality of locations with respect to said part; an imaging detector for forming a plurality of measured x-ray images of said part, one such measured x-ray image corresponding to each of said illumination locations; and a controller for comparing each of said measured x-ray images with a corresponding calibration image, said controller providing a defective part indication if one of said measured x-ray images differs from said corresponding calibration image by more than a threshold value in part of said measured x-ray image.