A CT scanner and method of operating the CT scanner enables customized automated selection of tube current and peak tube voltage for a CT scan. The CT scanner receives data, each datum of which corresponds to a reference image quality (noise level at a certain tube voltage) for patient water equivalent diameter (“WED”) body size. The CT scanner then stores the noise level and patient WED, and a processor in the CT scanner generates a curve corresponding to acceptable noise levels as a function of water equivalent diameter. The CT scanner stores the curve in a memory associated with the scanner and the CT scanner is subsequently operated with reference to the curve stored in the memory. The tube voltage that can generate the reference CT scan quality (signal-to-noise ratio) with the lowest radiation dose to the patient is selected.
