The invention relates to a modification arrangement for an X-ray generating device, a modification method, a computer program element for controlling such device and a computer readable medium having stored such computer program element. The modification arrangement comprises a cathode, an anode (2) and modification means, e.g. a modification device. The cathode is configured to provide an electron beam (15). The anode (2) is configured to rotate under impact of the electron beam (15) and is segmented by slits (21) arranged around the anode's circumference. The modification means are configured to modify the electron beam (15) when the electron beam (15) is hitting one of the anode's rotating slits (21).