1. A method for acquiring an image of a 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; b) determining an initial intravenous (IV) contrast volume from at least the scout data; c) prescribing a reference scanning protocol for a clinical task to be implemented using the CT system to image the subject; d) determining a radiation dose reduction relative to the reference scanning protocol that corresponds to an acceptable image contrast for the clinical task; e) determining a reduced intravenous contrast volume associated with the radiation dose reduction using a computed tomography dose index; f) adjusting the reference scanning protocol prescribed in step c) using the reduced IV contrast volume determined at step e); and g) acquiring imaging data of the subject using the CT system using the adjusted scanning protocol.