The present invention relates to an apparatus (10) for X-ray dual energy data processing. It is described to provide (210) a processing unit (30) with at least one first emission spectrum characteristic of an X-ray tube operating in a first mode of operation. The processing unit is provided (220) with at least one second emission spectrum characteristic of the X-ray tube operating in a second mode of operation. The at least one first emission5 spectrum is different to the at least one second emission spectrum. The processing unit is provided (230) with at least two images acquired by a CT scanner acquiring interleaved projection image data where an X-ray tube is operating back and forth from the first mode of operation to the second mode of operation. A first image of the at least two images was captured by a detector of the CT scanner from X-rays produced by the X-ray tube operating in the first mode of operation and a second image of the at least two images was captured by the detector from X-rays produced by the X-ray tube operating in the second mode of operation. The processing unit is provided (240) with an afterglow function that models afterglow of the detector. The processing unit determines (250) two basis function images, the determination comprising utilizing the first image, the second image, the at least one first emission spectrum, the at least one second emission spectrum and the afterglow function.La présente invention concerne un appareil (10) destiné au traitement de données d'énergie double de rayons X. L'invention concerne (210) une unité de traitement (30) ayant au moins une première caractéristique de spectre d'émission d'un tube à rayons X fonctionnant selon un premier mode de fonctionnement. L'unité de traitement est pourvue (220) d'au moins une seconde caractéristique de spectre d'émission du tube à rayons X fonctionnant selon un second mode de fonctionnement. Le ou les premiers spectres d'émission sont différents du ou des seconds spectres
