Patent ID: 7158611

Claim:
A method for determining distributions of density and atomic number in an object to be examined, comprising: recording a first distribution of X-ray absorption values of the object to be examined using a first X-ray spectrum; recording at least a further distribution of X-ray absorption values of the object to be examined using a further X-ray spectrum; selecting, from the recorded first distribution of X-ray absorption values, a first X-ray absorption value; selecting from the recorded further distribution of X-ray absorption values, a further X-ray absorption value assigned to said first X-ray absorption value or selecting, from each of said recorded further distribution of X-ray absorption values, a further X-ray absorption value assigned to said first X-ray absorption value; specifying a first function representing paired values of density and atomic number that correspond to said first X-ray absorption value selected from said recorded first distribution of X-ray absorption values; specifying a further function representing paired values of density and atomic number that correspond to said further X-ray absorption value selected from said recorded further distribution of X-ray absorption values of specifying a further function representing paired values of density and atomic number for each X-ray absorption value assigned to said first X-ray absorption value in the recorded further distributions of X-ray absorption values; and determining a value for the density and determining a value for the atomic number from a comparison of said first function representing paired values of density and atomic number that correspond to said first X-ray absorption value with one or more of said further functions representing paired values of density and atomic number that correspond to said respective further X-ray absorption values, and which are assigned to said first X-ray absorption value.