  X-ray phase contrast imaging offers a way to visualize the internal
structures of an object without the need to deposit any radiation, and thereby
alleviate the main concern in x-ray diagnostic imaging procedures today.
Grating-based differential phase contrast imaging techniques are compatible
with compact x-ray sources, which is a key requirement for the majority of
clinical x-ray modalities. However, these methods are substantially limited by
the need for mechanical phase stepping. We describe an electromagnetic phase
stepping method that eliminates mechanical motion, and thus removing the
constraints in speed, accuracy and flexibility. The method is broadly
applicable to both projection and tomography imaging modes. The transition from
mechanical to electromagnetic scanning should greatly facilitate the
translation of x-ray phase contrast techniques into mainstream applications.
