1. A method of determining a distribution of a contrast medium in a tissue structure, an X-ray scan being performed during the presence of the contrast medium, comprising: measuring absorption data for at least two different energy spectra; reconstructing a computed tomography intermediate image per energy spectrum; determining the distribution of the contrast medium in the tissue structure from different energy-specific absorption behavior between the tissue structure and the contrast medium, and a calculating significancy statement referring to the distribution of the contrast medium from the at least two intermediate images, by forming the quotient of the intermediate images.