1. A computer-readable medium storing computer-executable instructions that when executed by a computer cause the computer to perform a method, the method comprising: accessing an under-sampled data set that is associated with a scan of an object to be imaged performed by a medical imaging apparatus; producing an under-sampled approximation of the under-sampled data from previously acquired data; producing a sparsified data set from the under-sampled approximation and the under-sampled data set; producing a fully-sampled approximation of the under-sampled raw data set; and storing the sparsified data set on a computer-readable medium.