A method and apparatus is disclosed to acquire scout scan data of a subject and analyzed to determine a peak-to-peak modulation amplitude of a normalized waveform indicative of subject size and shape. The scout scan data provides a representation of patient size and shape that is associated with an ideal tube current modulation waveform or profile. The ideal tube current modulation profile may then be sampled or approximated at various points to determine a tube current modulation profile for implementation to acquire CT data with reduced dose but without sacrificing image quality.