Modification and elimination of back projection weight during the CT image reconstruction
View Patent ↗At least one embodiment of the invention relates to a method for the reconstruction of image data from an examined object, using measuring data, wherein the measuring data were first recorded during a relative movement between a radiation source on a computer tomography system and the examined object. In at least one embodiment, the image reconstruction is based on a back projection of the filtered measuring data. During the back projection, a back projection weight that depends on the respective image point is used and the power with which the back projection weight is used is selectable.
1. A method for the reconstruction of image data of an examined object from measuring data, the measuring data being recorded with a detector during a relative movement between a radiation source of a computer tomography system and the examined object, the method comprising:
basing the image reconstruction on a back projection of filtered measuring data;
realizing the back projection using a back projection weight which depends on a location of a respective point of the image data; and
selecting a power with which the back projection weight is used, wherein
a differentiation according to the method of the finite differences is realized, using supporting points for filtering the measuring data,
a distance between supporting points contain a term that depends on the location of the respective image point and corresponds to the back projection weight, and
a power of the term follows from the selected power of the back projection weight.
2. The method according to claim 1 , wherein the power of the back projection weight is 2−p and the power of the term is p, and
p has a selectable nonzero value.
3. The method according to claim 1 , wherein the dependence on the location ( x ) of the respective image point is derived from the term x · e w wherein x indicates the location ( x ) of the respective image point and e w indicates a direction perpendicular to the surface of the detector.
4. The method according to claim 1 , wherein the measuring data are recorded during a relative movement of the radiation source around the examined object, and
the movement amounts to less than one complete rotation.
5. The method according to claim 1 , wherein the measuring data are detected in a fan-beam geometry and used for reconstructing two-dimensional image data of the examined object.
6. The method according to claim 1 , wherein the measuring data are detected in a cone-beam geometry and used for reconstructing three-dimensional image data of the examined object.
7. The method according to claim 1 , wherein the image reconstruction from the measuring data is realized without prior conversion to the parallel beam geometry.
8. The method according to claim 1 , wherein the using of supporting points includes using two supporting points.
9. A computer and control unit for reconstruction of image data of an examined object from measuring data from a computer tomography (CT) system, said computer and control unit comprising:
a program memory for storing program code segments, wherein the program code segments stored in the program memory, when executed by a processor, are used to realize a method according to claim 1 .
10. A non-transitory computer-readable medium including a computer program product, the computer program product comprising instructions which when executed by a processor, causes the processor to carry out functions including:
basing an image reconstruction of an examined object from measuring data on a back projection of filtered measuring data, the measuring data being recorded with a detector during a relative movement between a radiation source of a computer tomography system and the examiner object;
realizing the back projection using a back projection weight which depends on a location of a respective point of the image data; and
selecting a power with which the back projection weight is used, wherein
a differentiation according to the method of the finite differences is realized, using supporting points for filtering the measuring data,
a distance between supporting points contain a term that depends on the location of the respective image point and corresponds to the back projection weight, and
a power of the term follows from the power of the back projection weight.
11. A computer tomography system, comprising:
a computer; and
a control unit in communication with the computer, the control unit configured to carryout functions including:
basing an image reconstruction of an examined object from measuring data on a back projection of filtered measuring data, the measuring data being recorded with a detector during a relative movement between a radiation source of the computer tomography system and the examined object,
realizing the back projection using a back projection weight which depends on a location of a respective point of the image data, and
selecting a power with which the back projection weight is used, wherein
a differentiation according to the method of the finite differences is realized, using supporting points for filtering the measuring data,
a distance between supporting points contain a term that depends on the location of the respective image point and corresponds to the back projection weight, and
a power of the term follows from the power of the back projection weight.