[Dose output at an image intensifier with peak value- or mean value-control]

X-ray fluoroscopy equipment with automatic brightness control works either on the principle of peak value control or mean value control. The different modes of operation of both control types have the consequence that different dose rate values are regulated if a homogeneous phantom is used. The controlled value using peak value control lies a factor of 1.4 higher than by mean value control. A theoretical consideration about the effect of different dose rate contrast distributions at the image intensifier with regard to the peak and mean values of both types of brightness control results in conditions, which an inhomogeneous phantom must satisfy to yield the same mean dose rate in both cases. By means of an inhomogeneous phantom construction in accordance with these conditions it is possible to compare the dose rate and also image quality parameters of different X-ray units with different types of brightness control.