This invention is a test object for phase contrast x-ray imaging, which is used to test that artifacts which may adversely affect the scatter measurement have been properly removed. The test object consists of three or more materials which are homogeneous, with no large density variations on length scales between 10 nm and 200 microns, and represent a range of atomic numbers. The materials are machined to a thickness suited to the energy of the x-rays used, such that 10-90% of the beam intensity is transmitted through the object. A phase contrast measurement is performed, with corrections for spurious signals due to spectral changes during attenuation, and the resulting scatter image of the test object will be consistent with background if the correction is successful.