1. A method, comprising: performing a three dimensional volume scan of a region of interest located in a portion of an object or subject in an examination region, including dynamically collimating a radiation beam used to perform the scan so that a geometry and/or location of the radiation beam tracks, during the scan, to a geometry and/or location of the region of interest, wherein the region of interest is a sub-region of the portion of the object or subject in the examination region.