1. A method comprising: receiving, at an extrapolation processor, a CT projection for extrapolation; selecting a target patch comprising at least one pixel of a row to be extrapolated; forming an initialized target patch by setting the at least one pixel to be either zero or set equal to a neighboring pixel; generating a correlation profile between the initialized target patch and one or more source patches, wherein the source patches comprise measured pixels in the CT projection in one or more rows adjacent to the target patch and not including any area of the target patch; and generating projection data for the at least one pixel of the target patch based on the correlation profile and the measured pixels of at least one of the one or more source patches.