1. A system for obtaining an image, comprising: a processor for receiving a projection image, wherein the projection image is generated using a flat panel and a radiation source that is configured to provide a radiation beam, processing the projection image to obtain a filtered image by applying filtering to one or more portions of the projection image having one or more attenuation values that exceed a prescribed threshold, applying a first factor for the projection image to obtain a first weighted image, applying a second factor for the filtered image to obtain a second weighted image, and obtaining a corrected image using the first and second weighted images; and a medium for storing the corrected image; wherein the processor is configured to determine the prescribed threshold based at least in part on one or more of maximal attenuation values of previously acquired projection images, and wherein one of the previously acquired projection images comprises attenuation values that exceed the prescribed threshold.