The image noise. The image noise at 80 kV and 120 kV is shown for different tube currents. From the regression equations one can see that the tube current must be increased from 160 mA to 675 mA when changing the tube voltage from 120 kV to 80 kV to attain the same image noise of 15 HU.
Holm et al. BMC Medical Imaging 2012 12:20 doi:10.1186/1471-2342-12-20