Method and system for substantially reducing artifacts in circular cone beam computer tomography (CT)
View Patent ↗Cone beam artifacts arise in circular CT reconstruction. The cone beam artifacts are substantially removed by reconstructing a reference image from measured data at circular source trajectory, generating synthetic data by forward projection of the reference image along a pre-determined source trajectory, which supplements the circular source trajectory to a theoretically complete trajectory, reconstructing a correction image from the synthetic data and substantially reducing the cone beam artifacts by generating a corrected image using the reference image and the correction image.
1. A method of correcting cone beam artifacts in circular computed tomography, comprising the steps of:
a) reconstructing a reference image from measured data at a predetermined circular source trajectory, the reference image being obtained based upon a filtered-backprojection algorithm by filtering along predetermined filtering directions, the predetermined filtering directions being given by Cseg+z/cos (gamma), where gamma is a cone angle, z is a vertical distance from Cseg, which is defined by a number of detector rows—1 divided by 2;
b) generating synthetic data by forward projection of the reference image along a predetermined source trajectory, which supplements the circular source trajectory to a theoretically complete trajectory;
c) reconstructing a correction image from the synthetic data; and
d) substantially reducing the cone beam artifacts by generating a corrected image using the reference image and the correction image.
2. The method of correcting cone beam artifacts in circular computed tomography according to claim 1 wherein the reference image is one of a circular Feldkamp (CFK) image and a Hybrid convolution reconstruction (Hconv) image.
3. The method of correcting cone beam artifacts in circular computed tomography according to claim 1 wherein the correction image is a line scan reconstruction image.
4. The method of correcting cone beam artifacts in circular computed tomography according to claim 1 further comprising additional step f) of iterating the steps b) through d) using the corrected image as the reference image in the step b) for a predetermined number of times.
5. The method of correcting cone beam artifacts in circular computed tomography according to claim 1 wherein a low pass filter is applied in the step b).
6. The method of correcting cone beam artifacts in circular computed tomography according to claim 1 wherein the step a) generates a first circular image and a second circular image from the measured circular data, the first circular image has a full field of view while the second circular image is a desired field of view.
7. The method of correcting cone beam artifacts in circular computed tomography according to claim 6 wherein the step b) applies a predetermined OSR filter to the first circular image.
8. The method of correcting cone beam artifacts in circular computed tomography according to claim 7 wherein the step b) forward projects the first circular image to generate forward projected line data.
9. The method of correcting cone beam artifacts in circular computed tomography according to claim 8 wherein the step c) reconstructs an line image from the forward projected line data.
10. The method of correcting cone beam artifacts in circular computed tomography according to claim 9 wherein the step d) substantially reduces the cone beam artifacts by generating the corrected image using the second circular image and the line image.
11. The method of correcting cone beam artifacts in circular computed tomography according to claim 10 further comprising additional step f) of iterating the steps b) through d) using the corrected image as the reference image in the step b) for a predetermined number of times.
12. A system for correcting cone beam artifacts in circular computed tomography, comprising:
a reconstruction device for reconstructing a reference image from measured data at a predetermined circular source trajectory, the reference image being obtained based upon a filtered-backprojection algorithm by filtering along predetermined filtering directions, the predetermined filtering directions being given by Cseg+z/cos (gamma), where gamma is a cone angle, z is a vertical distance from Cseg, which is defined by a number of detector rows—1 divided by 2; and
a cone beam artifact reduction device connected to said reconstruction device for generating synthetic data by forward projection of the reference image along a predetermined source trajectory, which supplements the circular source trajectory to a theoretically complete trajectory, wherein said reconstruction device reconstructs a correction image from the synthetic data and said cone beam artifact reduction device substantially reduces the cone beam artifacts by generating a corrected image using the reference image and the correction image.
13. The system for correcting cone beam artifacts in circular computed tomography according to claim 12 wherein the reference image is one of a circular Feldkamp (CFK) image and a Hybrid convolution reconstruction (Hconv) image.
14. The system for correcting cone beam artifacts in circular computed tomography according to claim 12 wherein the correction image is a line scan reconstruction image.
15. The system for correcting cone beam artifacts in circular computed tomography according to claim 12 wherein said reconstruction device and said cone beam artifact reduction device iterate for a predetermined number of iterations using the corrected image as the reference image.
16. The system for correcting cone beam artifacts in circular computed tomography according to claim 12 wherein said reconstruction device utilizes a low pass filter.
17. The system for correcting cone beam artifacts in circular computed tomography according to claim 12 wherein said reconstruction device generates a first circular image and a second circular image from the measured circular data, the first circular image has a full field of view while the second circular image is a desired field of view.
18. The system for correcting cone beam artifacts in circular computed tomography according to claim 17 wherein said cone beam artifact reduction device applies a predetermined OSR filter to the first circular image.
19. The system for correcting cone beam artifacts in circular computed tomography according to claim 18 wherein said cone beam artifact reduction device forward projects the first circular image to generate forward projected line data.
20. The system for correcting cone beam artifacts in circular computed tomography according to claim 19 wherein said reconstruction device reconstructs an line image from the forward projected line data.
21. The system for correcting cone beam artifacts in circular computed tomography according to claim 20 wherein said cone beam artifact reduction device substantially reduces the cone beam artifacts by generating the corrected image using the second circular image and the line image.
22. The system for correcting cone beam artifacts in circular computed tomography according to claim 21 wherein said reconstruction device and said cone beam artifact reduction device iterate for a predetermined number of iterations using the corrected image as the reference image.