Method and system for computed tomographic imaging
The present invention is a method and system for computed tomography imaging. The system for computed tomography imaging may comprise: a) an x-ray source; b) an x-ray detector; and c) a processing unit, wherein the processing unit is configured to carry out the steps: i) obtaining CT projections of an object, the projections comprising at least one truncated projection; ii) calculating material-equivalent thickness (MET) values for the truncated projection; iii) establishing parameterized point-pairs separated in distance by the MET values; iv) fitting the parameterized point-pairs to a parameterized curve or to a set of curves according to a set of constraints on spatial relationships between the point-pairs; v) completing the truncated projections; and vi) reconstructing a CT image from non-truncated projections and the completed truncated projections.
1. A method for computed tomography (CT) imaging, the method comprising the steps:
obtaining CT projections of an object, the projections comprising at least one truncated projection;
calculating material-equivalent thickness (MET) values for the truncated projection;
establishing parameterized point-pairs separated in distance by the MET values;
fitting the parameterized point-pairs to a parameterized curve or to a set of curves according to a set of constraints on spatial relationships between the point-pairs;
completing the truncated projection; and
reconstructing a CT image from non-truncated projections and the completed truncated projection.
2. The method of claim 1 ,
wherein the step of calculating the MET values for the truncated projection comprises the steps:
fitting a primary transmission model for propagation through a material having a composition analogous to that of the object to a resultant imaging beam; and
converting measured x-ray transform values into a MET value.
3. The method of claim 1 ,
wherein the step of calculating the MET values for the truncated projection comprises the step:
obtaining fan or cone beam computed tomography projections.
4. The method of claim 1 ,
further comprising the step:
correcting MET values for anomalous portions of the object.
5. The method of claim 4 ,
wherein the step of correcting MET values further comprises the step:
modifying a sinogram by replacing a first ray sample with a second ray sample;
reconstructing the modified sinogram.
6. The method of claim 4 ,
wherein the step of correcting MET values further comprises the step:
substituting an air volume thickness for the MET.
7. The method of claim 1 ,
wherein the parameterized curve is an ellipse.
8. The method of claim 1 ,
wherein the step of fitting the parameterized point-pairs to a parameterized curve further comprises the step:
calculating a metric correlating the goodness-of-fit between the parameterized point-pairs and the parameterized curve.
9. The method of claim 8 ,
wherein the metric is the squared norm of a vector of plurality of vectors,
wherein the vector of the plurality of vectors joins a point of a parameterized point-pair to the parameterized curve,
wherein the vector of the plurality of vectors intersects the centroid of the parameterized curve.
10. The method of claim 9 , further comprising the step:
minimizing a sum of the squared norms the plurality of the vectors.
11. A non-transitory computer readable storage medium having computer readable instructions for carrying out a method for computed tomography (CT) imaging, the method comprising the steps:
obtaining CT projections of an object, the projections comprising at least one truncated projection;
calculating material-equivalent thickness (MET) values for the truncated projection;
establishing parameterized point-pairs separated in distance by the MET values;
fitting the parameterized point-pairs to a parameterized curve or to a set of curves according to a set of constraints on spatial relationships between the point-pairs;
completing the truncated projection; and
reconstructing a CT image from non-truncated projections and the completed truncated projection.
12. The computer readable storage medium of claim 11 ,
wherein the step of calculating the MET values for the truncated projection comprises the steps:
fitting a primary transmission model for propagation through a material having a composition analogous to that of the object to the resultant imaging beam; and
converting measured x-ray transform values into METs.
13. The computer readable storage medium of claim 11 ,
wherein the step of calculating the MET values for the truncated projection comprises the step:
obtaining fan or cone beam computed tomography projections.
14. The computer readable storage medium of claim 11 , further comprising the step:
correcting MET values for anomalous portions of the object.
15. The computer readable storage medium of claim 14 ,
wherein the step of correcting MET values further comprises the step:
modifying a sinogram by replacing a first ray sample with a second ray sample;
reconstructing the modified sinogram.
16. The computer readable storage medium of claim 14 ,
wherein the step of correcting MET values further comprises the step:
substituting an air volume thickness for the MET.
17. The computer readable storage medium of claim 11 ,
wherein the parameterized curve is an ellipse.
18. The computer readable storage medium of claim 11 ,
wherein the step of fitting the parameterized point-pairs to a parameterized curve further comprises the step:
calculating a metric correlating the goodness-of-fit between the parameterized point-pairs and the parameterized curve.
19. The computer readable storage medium of claim 11 ,
wherein the metric is a squared norm of a vector of plurality of vectors,
wherein the vector of the plurality of vectors joins a point of a parameterized point-pair to the parameterized curve,
wherein the vector of the plurality of vectors intersects the centroid of the parameterized curve.
20. The computer readable storage medium of claim 11 , further comprising the step:
minimizing a sum of the squared norms the plurality of the vectors.
21. A system for CT imaging, the system comprising:
an x-ray source;
an x-ray detector; and
a processing unit,
wherein the processing unit is configured to carry out the steps:
obtaining CT projections of an object, the projections comprising at least one truncated projection;
calculating material-equivalent thickness (MET) values for the truncated projection;
establishing parameterized point-pairs separated in distance by the MET values;
fitting the parameterized point-pairs to a parameterized curve or to a set of curves according to a set of constraints on spatial relationships between the point-pairs;
completing the truncated projection; and
reconstructing a CT image from non-truncated projections and the completed truncated projection.
22. The system of claim 21 ,
further comprising the step:
correcting MET values for anomalous portions of the object.
23. The system of claim 22 ,
wherein the step of correcting MET values further comprises the step:
modifying a sinogram by replacing a first ray sample with a second ray sample;
reconstructing the modified sinogram.
24. The system of claim 22 ,
wherein the step of correcting MET values further comprises the step:
substituting an air volume thickness for the MET.