A radiographic imaging apparatus comprising an X-ray source (20, 108) for projecting X-ray radiation into an examination region (30, 106) and a photon counting X-ray detector (40, 110) for receiving X-ray radiation after passing through said examination region and converting the received X-ray radiation into detector signals, wherein said X-ray source (20, 108) comprises - a cathode for emitting an electron beam, - a rotary X-ray anode having a number of radial slits and a target layer provided on a surface of said rotary X-ray anode in between said radial slits for emitting X-ray radiation when hit by said electron beam, and - a drive unit for rotating said X-ray anode, and wherein said photon counting X-ray detector (40, 110) comprises - a direct conversion X-ray detection unit for receiving the X-ray radiation and outputting an electrical signal, - a photon counting unit for generating, from said electrical signal, said detector signal representing the number of photons of the received X-ray radiation, and - a persistent current sensing and correction unit for sensing a persistent output current in a blanking interval during which no X-ray radiation is emitted by said X-ray source and for using the sensed persistent output current to correct a detector signal generated by said photon counting unit in a subsequent measurement interval during which X-ray radiation is emitted by said X-ray source; wherein said persistent current sensing and correction unit comprises - an amplifier coupled between the output of said direct conversion X-ray detection unit and the input of said photon counting unit for amplifying said electrical signal, and - a sample and hold unit for receiving said amplified electrical signal and generating, during the blanking interval, a compensation signal coupled to the output of said direct conversion X-ray detection unit for dynamically adjusting the electrical signal to compensate the persistent output current, comprising a switch for enabling a dynamic adjustment of the electrical signal during a blanking interval by use of the dynamically generated compensation signal and for keeping the compensation signal constant during a subsequent measurement interval, characterized in that the switch is controlled by a blanking signal to be asynchronously with the measurement intervals of the photon counting X-ray detector and wherein a reference measurement is used to correct for X-ray flux variation caused by flux blanking. - a cathode for emitting an electron beam, - a rotary X-ray anode having a number of radial slits and a target layer provided on a surface of said rotary X-ray anode in between said radial slits for emitting X-ray radiation when hit by said electron beam, and - a drive unit for rotating said X-ray anode, - a direct conversion X-ray detection unit for receiving the X-ray radiation and outputting an electrical signal, - a photon counting unit for generating, from said electrical signal, said detector signal representing the number of photons of the received X-ray radiation, and - a persistent current sensing and correction unit for sensing a persistent output current in a blanking interval during which no X-ray radiation is emitted by said X-ray source and for using the sensed persistent output current to correct a detector signal generated by said photon counting unit in a subsequent measurement interval during which X-ray radiation is emitted by said X-ray source; - an amplifier coupled between the output of said direct conversion X-ray detection unit and the input of said photon counting unit for amplifying said electrical signal, and - a sample and hold unit for receiving said amplified electrical signal and generating, during the blanking interval, a compensation signal coupled to the output of said direct conversion X-ray detection unit for dynamically adjusting the electrical signal to compensate the persistent output current, comprising a switch for enabling a dynamic adjustment of the electrical signal during a blanking interval by use of the dynamically generated compensation signal and for keeping the compensation signal constant during a subsequent measurement interval,