Patent DE-102005049586-A1 (DE)
Title: Method for generating computerized tomography displays in x-ray computed tomography, comprises scanning an object and reconstructing a first computerized tomography display from an absorption data of an energy spectrum
Inventor: FLOHR THOMAS
IPC: A61B6/03
Filed: 2005-10-17
Abstract: The method for generating computerized tomography (CT) displays in x-ray computed tomography, comprises scanning an object, reconstructing a first CT display from an absorption data of an energy spectrum, determining a material thickness of the first material/first material composition for each scanning beam in space on the basis of the first CT display, calculating a virtual attenuation value, and reconstructing a second CT display with the aid of the virtual attenuation values. The method for generating computerized tomography (CT) displays in x-ray computed tomography, comprises scanning an object, reconstructing a first CT display from an absorption data of an energy spectrum, determining a material thickness of the first material/first material composition for each scanning beam in space on the basis of the first CT display, calculating a virtual attenuation value, and reconstructing a second CT display with the aid of the virtual attenuation values. The scanning of an object is composed of N+1 materials/material compositions with different absorption coefficients, by revolving ray fans that generates a multiplicity of scanning beams in space with N>=2 different energy spectra. The first CT display is reconstructed from the absorption data of the energy spectrum and the first material/first material composition, which is segmented from knowledge of its absorption coefficient. The material thicknesses of the other materials/material compositions are determined for each scanning beam in space, by a known absorption of the first material from the spatially identical scanning beams of different energy spectra. The virtual attenuation value is calculated for each scanning beam in space from the N+1 known material thicknesses with the aid of newly defined absorption coefficients. The span values of the newly defined absorption coefficients are smaller than the span values of the absorption coefficients of the N+1 materials/material compositions. Third CT display is generated by superposing the segmented first CT display on the second CT display. A lookup table is made available for determining the material thicknesses of N other different materials/material compositions on the basis of a known material thickness of the first material as a function of the absorption values of N energy spectra. The intermediate values are missed in the lookup table are determined by interpolation. The lookup table is determined by calculating an absorption measurements with the aid of the energy spectra used at different material thicknesses of the considered materials/material compositions. The determination of the material thicknesses of N other different materials/material compositions is performed by solving a system of equations with N absorption equations and N unknown material thicknesses by a known absorption coefficients of the materials/material compositions as the function of the energy spectra. The segmentation of the first material/first material composition is performed by setting an upper and a lower limiting value for the absorption coefficient. The first, second and third material composition consists of calcium, iodine and water. A color is assigned to the material/material composition in the CT display. The different energy spectra are generated by a single focus/detector system. An independent claim is included for a computer readable medium.