Abstract: An X-ray examination apparatus arranged with control means to control a dose of an X-ray source in accordance with a grey-level distribution of an acquired image. The X-ray examination apparatus (1) comprises the X-ray unit (2) arranged to communicate data to the control and processing means (10). The X-ray unit (2) is arranged to generate a beam of X-rays (1f) propagating from an X-ray source (1c). The X-ray source (1c) together with the X-ray detector (1b)can be rotated about an acquisition volume V about a rotation axis (1e). The control and processing means (10) comprises an image processing means (3), which is arranged to compress the first image into the second image. Upon a compression of the first image with the grey-level compression function the resulting second image is forwarded to the control means (6), which is arranged to compute an average pixel value of the second image and to compare it with a pre-stored reference value.