1. A computer implemented method of registering a first energy projection radiographic image (I IN ) to a second energy projection radiographic image (I REF ) comprising: (a) selecting a first dimension size for corresponding regions of interest in I IN and I REF ; (b) selecting a first region of interest from the corresponding regions of interest having the first dimension size in both I IN and I REF ; (c) applying a deformation operation to the first region of interest in I IN ; (d) utilizing a registration metric that quantifies a degree of registration; (e) identifying an optimal deformation operation that optimizes the registration metric; (f) applying steps (b) through (e) for consecutive different ones of the corresponding regions of interest in I IN and I REF to register the entire I IN to I REF ; (g) interpolating results of the optimal deformation operation to remove discontinuities between the corresponding regions of interest to create an output image (I OUT ) that is more registered to I REF than I IN ; and (h) repeating steps (a) through (g) with a second dimension size for new corresponding regions of interest to iteratively register the I OUT created in step (g) to I REF .