An apparatus includes a computed tomography (CT) scanner (10), a reconstructor (46), a polychromatic corrector (50), a material classifier (54) and an image processor (60). The scanner provides spectral CT information. The reconstructor (46) reconstructs the data from the CT scanner (10) into a volume space. The material classifier (54) determines a material composition of locations in the volume space as a function of their location in an attenuation space. Information indicative of the material composition is presented ON a display (62).
