Computed-tomography system and method for determining volume information for a body

A computed-tomography system, comprising:

• a data-processing device, and
• an x-ray detector coupled to the data-processing device, wherein a real projection-image data is produced by the x-ray detector, and wherein the data-processing device is configured to execute a method of determining volume information of a body comprising:
• specifying initial voxel data for a plurality of voxels of the body,
• generating synthetic projection-image data based upon the initial voxel data with a projection rule modeling a course of the radiation-based projection method,
• comparing the synthetic projection-image data with the real projection-image data and determining projection-error data,
• imaging the projection-error data on the basis of a back-projection rule dependent on the projection rule and generating voxel-error data,
• determining correction data from the voxel-error data by a gradient-based optimizing algorithm, and
• determining corrected voxel data based upon the correction data,
• wherein a sequence of method-specific steps is performed repeatedly, wherein previously determined corrected voxel data is used as initial voxel data in a repeated step,
• wherein, after the method-specific steps are performed at least once, the correction data is determined in the repeated step only for a subset of the voxel-error data having negative values,
• wherein a mathematical model for describing a time dependency of the voxel data is defined for at least one voxel of the body,
• wherein the model includes at least one model parameter,
• wherein an update vector data is computed by solving the mathematical model,
• wherein the update vector data comprises at least one correction value, and
• wherein the least one correction value is added to the at least one model parameter to generate the corrected voxel data for a further iteration step.

A non-transitory computer readable medium storing instructions which, when executed on a computer, perform a method of determining volume information of a body, wherein the instructions comprising:

• a computer program for:
• specifying initial voxel data for a plurality of voxels of the body,
• generating synthetic projection-image data based upon the initial voxel data with a projection rule modeling a course of the radiation-based projection method,
• comparing the synthetic projection-image data with a real projection-image data obtained from a radiation-based projection method and determining projection-error data,
• imaging the projection-error data on the basis of a back-projection rule dependent on the projection rule and generating voxel-error data,
• determining correction data from the voxel-error data by a gradient-based optimizing algorithm, and
• determining corrected voxel data based upon the correction data,
• wherein a sequence of method-specific steps is performed repeatedly, wherein previously determined corrected voxel data is used as initial voxel data in a repeated step,
• wherein, after the method-specific steps are performed at least once, the correction data is determined in the repeated step only for a subset of the voxel-error data having negative values,
• wherein a mathematical model for describing a time dependency of the voxel data is defined for at least one voxel of the body,
• wherein the model includes at least one model parameter,
• wherein an update vector data is computed by solving the mathematical model,
• wherein the update vector data comprises at least one correction value, and
• wherein the least one correction value is added to the at least one model parameter to generate the corrected voxel data for a further iteration step.