1. A method for acquiring an image of a region of interest (ROI) of subject using a computed tomography (CT) system, the method comprising: a) performing a scout scan of the subject using the CT system to yield scout data related to the ROI; b) determining an initial contrast volume form at least the scout data; c) prescribing a scanning protocol to be implemented using the computed tomography system to image the ROI; d) determining a size of the subject about the ROI; e) determining a computed tomography dose related to volume (CTDIvol) based on at least the size determined at step d); f) adjusting the scanning protocol prescribed in step b) to match at least one of a desired radiation dose and a relative intravenous (IV) contrast dose to a reference CTDIvol; and g) acquiring imaging data from the ROI using the CT system using the adjusted scanning protocol.