Method and CT system for topogram scanning
A method for improved utilization of a radiation dose applied to an examination object during topogram scanning of a CT system, and a CT system with a system axis using a cylindrical curved multi-row detector, are disclosed. In an embodiment, the method includes topogram scanning of the examination object with at least one emitter-detector combination disposed on a rotatable gantry from a predetermined rotation angle of the gantry, wherein during the topogram scanning a relative movement occurs between examination object and emitter-detector combination in the system axis direction; calculation of at least one flat image in at least two planes running in parallel to the system axis in each case by a tomosynthesis reconstruction; and storage and/or further processing of at least one of the flat images of the examination object to represent a topogram.
1. A method for improved utilization of a radiation dose applied to an examination object during topogram scanning of a CT system with a system axis using a cylindrical curved multi-row detector, comprising:
topogram scanning of the examination object with at least one emitter-detector combination disposed on a rotatable gantry from a rotation angle of the gantry, wherein during the topogram scanning a relative movement takes place between examination object and emitter-detector combination in the system axis direction;
calculating at least one flat image, in at least two respective planes running in parallel to the system axis, by a tomosynthesis reconstruction; and
at least one of storing and further processing at least one of the flat images of the examination object to represent a topogram.
2. The method of claim 1 , further comprising:
converting measured cylindrical projections of the cylindrical curved multi-row detector, before the tomosynthesis reconstruction, into flat projections.
3. The method of claim 1 , wherein a detector-side collimator, configured to restrict the rays at least in the direction of the system axis, is used for the topogram scanning.
4. The method of claim 1 , wherein a detector-side collimator, configured to which restrict the rays at least in the direction of rotation of the gantry, is used for topogram scanning.
5. The method of claim 1 , wherein, to represent the topogram, a single flat image is displayed in a slice plane in the examination object.
6. The method of claim 1 , wherein, to represent the topogram, a number of flat images in a number of slice planes in the examination object are displayed overlaid.
7. The method of claim 1 , wherein an x-ray tube, which forms a single fixed focus relative to the x-ray tube, is used as the emitter.
8. The method of claim 1 , wherein an x-ray tube, which forms a spring focus, is used as the emitter.
9. The method of claim 8 , wherein the spring focus assumes at least two different positions in the system axis direction relative to the x-ray tube during the scanning.
10. The method of claim 8 , wherein the spring focus assumes at least two different positions in the circumferential direction relative to the x-ray tube during the scanning.
11. The method of claim 1 , wherein a detector with more than six rows is used as the multi-row detector.
12. The method of claim 1 , wherein a preponderant number of the rays used for scanning are emitted at a taper angle of greater than 3°.
13. The method of claim 1 , further comprising obtaining depth information from the topogram scanning of the examination object.
14. The method of claim 2 , wherein a detector-side collimator, configured to restrict the rays at least in the direction of the system axis, is used for the topogram scanning.
15. The method of claim 2 , wherein a detector-side collimator, configured to which restrict the rays at least in the direction of rotation of the gantry, is used for topogram scanning.
16. The method of claim 2 , wherein, to represent the topogram, a single flat image is displayed in a slice plane in the examination object.
17. The method of claim 2 , wherein, to represent the topogram, a number of flat images in a number of slice planes in the examination object are displayed overlaid.
18. The method of claim 2 , wherein an x-ray tube, which forms a single fixed focus relative to the x-ray tube, is used as the emitter.
19. The method of claim 2 , wherein an x-ray tube, which forms a spring focus, is used as the emitter.
20. The method of claim 11 , a 64-row detector is used as the multi-row detector.
21. The method of claim 11 , a 128-row detector is used as the multi-row detector.
22. A CT system, comprising:
at least one emitter-detector combination, disposed on a gantry; and
a control and processing unit including a memory for storing program code, the program code being executable during operation to perform at least
topogram scanning of the examination object with at least one emitter-detector combination disposed on a rotatable gantry from a rotation angle of the gantry, wherein during the topogram scanning a relative movement takes place between examination object and emitter-detector combination in the system axis direction;
calculating at least one flat image, in at least two respective planes running in parallel to the system axis, by a tomosynthesis reconstruction; and
at least one of storing and further processing at least one of the flat images of the examination object to represent a topogram.