An imaging system includes a radiation source (110) that emits radiation that traverses an examination region and a detector (116) that detects radiation traversing the examination region and a subject disposed therein, and produces a signal indicative of the energy of the detected radiation. A data selector (122) energy discriminates the signal based on an energy spectra setting corresponding to first and second spectral characteristics of a contrast agent administered to the subject, wherein the contrast agent has a first attenuation spectral characteristic when attached to the target and a second different spectral characteristic when not attached to the target. A reconstructor (134) reconstructs the signal based on the first and second spectral characteristics and generates volumetric image data indicative of the target.
