The quantum-mechanical theoretical model for the quantitative description of phase contrast images from non-crystalline objects with arbitrary shapes has been developed. It takes into account multiple scattering effects both in the object (particularly, refraction and phase change) and in the crystals of monochromator and analyzer. Presence of homogeneously and inhomogeneously distributed microdefects and macrodeformations in monochromator-and analyzer-crystals, which influence significantly on the scattering pattern, has been taken into account.