Patent ID: 7856134

Claim:
A method for generating image data relating to a virtually prescribable X-ray tube voltage U 3 from first and second CT image data, wherein the first and second CT image data have been obtained by way of a computer tomograph by simultaneously, or nearly simultaneously, recording an object volume, the first CT image data describe a first distribution of the linear attenuation coefficient μ 1 (x) for a first X-ray spectrum S 1 , and the second CT image data describe a second distribution of the linear attenuation coefficient μ 2 (x) for a second X-ray spectrum S 2 , each voxel x of an object volume which is reconstructed from the first and second CT image data respectively being assigned the linear attenuation coefficients μ 1 (x) and μ 2 (x), and the first X-ray spectrum S 1 is assigned to a first X-ray tube voltage U 1 , and the second X-ray spectrum S 2 is assigned to a second X-ray tube voltage U 2 , in which case U 1 ≠U 2 , the method comprising: a) providing the first and second CT image data, b) prescribing the virtual X-ray tube voltage U 3 , where U 3 ≠U 1 and U 3 ≠U 2 , c) using the first and second CT image data for two prescribable base materials A, B to determine in each case a spatial density distribution ρ A (x), ρ B (x) assigned to the base materials A, B, in the reconstructed object volume, ρ(x)=ρ A (x)+ρ B (x) holding true for a density ρ(x) of a voxel x in the reconstructed object volume, d) providing an effective mass attenuation coefficient <α A > U 3 for the base material A, and an effective mass attenuation coefficient <α B > U 3 for the base material B, the effective mass attenuation coefficients <α A > U 3 and <α B > U 3 respectively being valid for an X-ray spectrum S 3 assigned to the virtual X-ray tube voltage U 3 , and e) determining the image data as a third distribution of effective linear attenuation coefficients μ 3 (x) in the reconstructed object volume in relation to the voltage U 3 on the basis of the following relationship: μ 3 ( x )=<α A > U 3 ·ρ A ( x )+<α B > U 3 ·ρ B ( x ).