1. A method for enhancing an image based on projection data comprising the steps of: a) projecting an x-ray beam through an object of interest to an x-ray detector, b) collecting x-ray attenuation data (projections) using an x-ray source and a detector at a plurality of positions around the object, c) estimating the orientation of structures within the obtained projection data, and d) adaptively filtering the x-ray attenuation data based on the locally estimated orientation of structures, wherein the adaptive filtering is in projection space, and e) reconstructing an image using the adaptively filtered x-ray attenuation data from step d).