The present invention relates to a CT system for determining the quantitative material concentrations of the components, such as bone, blood, contrast agent, in a region of interest of an object, such as a patient. To provide a CT system which improves the quality and explanatory power of quantitative material decomposition, a CT system is proposed comprising: a scanning unit (102) having a radiation source (10) and a detector unit (12) for acquisition of spectral CT projection data from said region of interest a modeling unit (104) for obtaining a photoelectric effect projection data set and a Compton effect projection data set by decomposing said spectral CT projection data set by means of respective models of photoelectric effect and Compton effect a reconstruction unit (106) for reconstructing a photoelectric effect image and a Compton effect image of said region of interest from said photoelectric effect projection data set and Compton effect projection data set a processing unit (108) for determining the concentrations of said components in said region of interest by solving a system of equations obtained by equating said photoelectric effect image data with the accumulated products of said concentrations and photoelectric attenuation coefficients for said components and equating said Compton effect image data with the accumulated products of said concentrations and Compton attenuation coefficients for said components. The invention relates further to a corresponding data processing device and method.La présente invention concerne un système de scanographie destiné à déterminer les concentrations quantitatives matérielles de composants, par exemple, dos, de sang ou dun agent de contraste chez un sujet dintérêt tel quun patient. Pour fournir un système de scanographie qui améliore la qualité et la portée de la composition quantitative matérielle, un système de scanographie comprend: une unité de balayage (102) possédant une source de rayonnement (10) et une uni
