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US 7,583,784 B2Granted
Method for calculating computed tomography pictures from detector data of a CT having at least two radiation sources
AssigneeSiemens Aktiengesellscahft
InventorLutz Andreas
Life of this patent
Estimating the term…
Abstract
A method is for calculating computed tomography pictures from detector data of a CT that uses at least two radiation sources that generate different conical beams. A spatial distribution of attenuation values of a scanned object is reconstructed with the aid of detector data of a first relatively large conical beam. The integral attenuation values that are required to supplement the relatively small conical beam are back calculated from the previously reconstructed data. Finally, a reconstruction of computed tomography pictures is subsequently carried out with the aid of the back calculated integral attenuation data and the measured integral attenuation data of the relatively small conical beam.
Claims21
A method for reconstructing computed tomography pictures from detector data of a CT that includes at least two radiation sources to generate conical beams, comprising:
- scanning an object, using at least two conical beams with fan angles of different sizes and measuring fields of different sizes, in at least one of a circular and spiral fashion, a first conical beam is larger than a second conical beam;
- measuring integral attenuation values of the first conical beam;
- reconstructing spatial attenuation values of the object by convolution and back projection using the measured integral attenuation values of at least the first conical beam that completely surrounds the object;
- scanning the object with the second conical beam, a measuring field of the second conical beam not completely surrounding the object;
- measuring integral attenuation values of the second conical beam;
- calculating an integral attenuation of virtual rays at least in an area outside of the measuring field of the second conical beam from the reconstructed spatial attenuation values of the area reconstructed using the measured integral attenuation values of the first conical beam;
- supplementing the measured integral attenuation values of the second conical beam with the calculated integral attenuation of the virtual rays at an edge of the second conical beam to provide a supplemented data set;
- reconstructing the spatial attenuation values of the object, at least in the measuring field of the second conical beam, based on the supplemented data set, to reconstruct the computed tomography pictures, wherein
- the at least two conical beams used, include different energy spectra, and the difference is considered when calculating the integral attenuation values of the virtual rays.
6 more elements
A computer-readable medium storing executable instructions which when executed by a computed tomography system causes the computed tomography system to perform a method comprising:
- scanning an object, using at least two conical beams with fan angles of different sizes and measuring fields of different sizes, in at least one of a circular and spiral fashion, a first conical beam is larger than a second conical beam;
- measuring integral attenuation values of the first conical beam;
- reconstructing spatial attenuation values of the object by convolution and back projection using the measured integral attenuation values of at least the first conical beam that completely surrounds the object;
- scanning the object with the second conical beam, a measuring field of the second conical beam not completely surrounding the object;
- measuring integral attenuation values of the second conical beam;
- calculating an integral attenuation of virtual rays at least in an area outside of the measuring field of the second conical beam from the spatial attenuation values of the area reconstructed using the measured integral attenuation values of the first conical beam;
- supplementing the measured integral attenuation values of the second conical beam with the calculated integral attenuation values of the virtual rays at an edge of the second conical beam to provide a supplemented data set;
- reconstructing the spatial attenuation values of the object, at least in the measuring field of the second conical beam, based on the supplemented data set, to reconstruct the computed tomography pictures, wherein
- the at least two conical beams used, include different energy spectra, and the difference is considered when calculating the integral attenuation values of the virtual rays.
6 more elements
A computed tomography system, comprising:
- at least two radiation sources to scan an object with at least two conical beams with fan angles of different sizes and measuring fields of different sizes, in at least one of a circular and spiral fashion, a first conical beam is larger than a second conical beam;
- means for measuring integral attenuation values of the at least two conical beams;
- means for reconstructing spatial attenuation values of the object by convolution and back projection using the measured integral attenuation values of at least the first conical beam that completely surrounds the object;
- means for scanning the object with the second conical beam;
- means for calculating an integral attenuation of virtual rays at least in an area outside of the measuring field of the second conical beam from the reconstructed spatial attenuation values of the area reconstructed using the measured integral attenuation values of the first conical beam;
- means for supplementing the measured integral attenuation values of the second conical beam with the calculated integral attenuation of the virtual rays at an edge of the second conical beam to provide a supplemented data set;
- and
- means for reconstructing the spatial attenuation values of the object, at least in the measuring field of the second conical beam, based on the supplemented data set, wherein
- the at least two conical beams used, include different energy spectra, and the difference is considered when calculating the integral attenuation values of the virtual rays.
6 more elements
Dependencies are inferred from the claim text.