1. A method of computer aided imaging, comprising: obtaining intensity data representing an intensity of radiation at a detector array, wherein a first dataset of the intensity data represents the intensity of the radiation at the detector array after propagating a first distance past an exit plane of an image volume, a second dataset of the intensity data represents the intensity of the radiation at the detector array after propagating a second distance past the exit plane of the image volume, and the first distance is greater than the second distance; determining, using a phase retrieval method and the intensity data, a phase of the radiation at the exit plane of the image volume; and reconstructing an image of a real part of an index of refraction of the image volume using an iterative reconstruction algorithm, including performing an affine projection of an image vector onto an affine space determined by a plurality of Radon transforms corresponding to the intensity data, and the image vector represents the real part of the index of refraction of the image volume.