A system and method of medical imaging is designed to reduce a patients X-ray exposure during scanning (112). The system automatically generates a default noise index (106) from a received set of scan parameter values that specifies a desired tube current of an X-ray source to use during the scanning of a patient. The default noise index (106) can then be overridden to select a preferred noise index based upon a desired diagnostic quality for a particular volume of interest (VOI) and a diagnostic objective.
