High pitch reconstruction of multislice CT scans

US 6,381,297 B1
Filed: 08/15/2000
Issued: 04/30/2002
Est. Priority Date: 08/15/2000
Status: Expired due to Fees

First Claim

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1. A method for generating an image of an object using a multislice computed tomography imaging system, said method comprising the steps of:

helically scanning an object with a multislice computed tomography imaging system to acquire projection data;

determining a set of conjugate samples of the projection data that formulate a set of parallel projections; and

reconstructing a set of images of the object using the conjugate samples.

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Abstract

One embodiment of the present invention is a method for generating an image of an object using a multislice computed tomography imaging system. The method includes steps of: helically scanning an object with a multislice computed tomography imaging system to acquire projection data; determining a set of conjugate samples of the projection data that formulate a set of parallel projections; and reconstructing a set of images of the object using the conjugate samples. By determining a set of conjugate samples that formulate a set of parallel projections, embodiments of the present invention make possible reconstruction of images from projection data scanned at 8:1 pitch or higher.

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22 Claims

1. A method for generating an image of an object using a multislice computed tomography imaging system, said method comprising the steps of:
- helically scanning an object with a multislice computed tomography imaging system to acquire projection data;
  
  determining a set of conjugate samples of the projection data that formulate a set of parallel projections; and
  
  reconstructing a set of images of the object using the conjugate samples.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
- - 2. A method in accordance with claim 1 wherein reconstructing a set of images of the object using the conjugate samples comprises the steps of weighting the parallel projections based on the conjugate samples, and reconstructing a set of images using the weighted parallel projections.
  - 3. A method in accordance with claim 1 wherein the multislice computed tomography imaging system comprises a detector having a plurality of parallel rows of detector elements configured to acquire projection data, and an x-ray source configured to project an x-ray beam, including an iso-ray, towards the detector through an object being scanned;
4. A method in accordance with claim 3 wherein reconstructing a set of images of the object from the set of parallel projections comprises the step of interpolating pairs of regions defined by the region boundaries to produce projections at a plane of reconstruction (POR).
5. A method in accordance with claim 4 wherein reconstructing a set of images of the object from the set of parallel projections comprises the step of applying a weighting function determined as a continuous function of a projection angle β
- to the projections at a plane of reconstruction for each image slice to be reconstructed.
6. A method in accordance with claim 5 wherein helically scanning an object with a multislice computed tomography imaging system to acquire projection data comprises the step of scanning the object at a helical pitch greater than 6:
- 1.
7. A method in accordance with claim 6 wherein helically scanning an object with a multislice computed tomography imaging system to acquire projection data comprises the step of scanning the object at a helical pitch of 8:
- 1.
8. A method in accordance with claim 7 wherein helically scanning an object with a multislice computed tomography imaging system to acquire projection data comprises the step of operating the computed tomography imaging system to acquire projection data representing four image slices, and wherein reconstructing a set of images of the object from the set of parallel projections comprises the step of reconstructing four images.
9. A method in accordance with claim 4 wherein helically scanning an object with a multislice computed tomography imaging system to acquire projection data comprises the step of operating the computed tomography imaging system to acquire projection data representing four image slices;
- wherein applying a weighting function determined as a continuous function of a projection angle β
  
  to the projections at a plane of reconstruction for each image slice to be reconstructed comprises the step of applying weighting functions written as;
  
  $\begin{matrix} w_{1} (β, γ) = {\begin{matrix} \frac{β - β_{4 -}^{'}}{β_{1}^{'} - β_{4 -}^{'}} & β_{4 -}^{'} \leq β < β_{1}^{'} \\ \frac{β - β_{2}^{'}}{β_{1}^{'} - β_{2}^{'}} & β_{1}^{'} \leq β < β_{2}^{'} \\ 0 & otherwise \end{matrix} \\ w_{2} (β, γ) = {\begin{matrix} \frac{β - β_{1}^{'}}{β_{2}^{'} - β_{1}^{'}} & β_{1}^{'} \leq β < β_{2}^{'} \\ \frac{β - β_{3}^{'}}{β_{2}^{'} - β_{3}^{'}} & β_{2}^{'} \leq β < β_{3}^{'} \\ 0 & otherwise \end{matrix} \\ w_{3} (β, γ) = {\begin{matrix} \frac{β - β_{2}^{'}}{β_{3}^{'} - β_{2}^{'}} & β_{2}^{'} \leq β < β_{3}^{'} \\ \frac{β - β_{4}^{'}}{β_{3}^{'} - β_{4}^{'}} & β_{3}^{'} \leq β < β_{4}^{'} \\ 0 & otherwise \end{matrix} \\ w_{4} (β, γ) = {\begin{matrix} \frac{β - β_{3}^{'}}{β_{4}^{'} - β_{3}^{'}} & β_{3}^{'} \leq β < β_{4}^{'} \\ \frac{β - β_{1 +}^{'}}{β_{4}^{'} - β_{1 +}^{'}} & β_{4}^{'} \leq β < β_{1 +}^{'} \\ 0 & otherwise \end{matrix} \end{matrix}$ where;
  
  w_i(β
  
  ,γ
  
  ) is a projection weighting function applied to a detector row i;
  
  γ
  
  is a detector angle;
  
  β
  
  _iis a projection angle at which an iso-ray of detector row i crosses a plane of reconstruction;
  
  β
  
  ′
  
  _i=β
  
  _i−
  
  γ
  
  is an angle of a parallel ray sample corresponding to a projection angle β
  
  _iof that sample; and
  
  β
  
  ′
  
  _i+=β
  
  ′
  
  _i+π and
  
  β
  
  ′
  
  _i−=β
  
  ′
  
  _i−
  
  π
  
  .
10. A method in accordance with claim 9 wherein helically scanning an object with a multislice computed tomography imaging system to acquire projection data comprises the step of scanning the object at a helical pitch greater than 6:
- 1.
11. A method in accordance with claim 10 wherein helically scanning an object with a multislice computed tomography imaging system to acquire projection data comprises the step of scanning the object at a helical pitch of 8:
- 1.

12. A multislice computed tomography system configured to:
- helically scan an object to acquire projection data;
  
  determine a set of conjugate samples of the projection data that formulate a set of parallel projections; and
  
  reconstruct a set of images of the object using the conjugate samples.
- View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
- - 13. A system in accordance with claim 12 wherein to reconstruct a set of images of the object using the conjugate samples, said system is configured to weight the parallel projections based on the conjugate samples, and to reconstruct a set of images using the weighted parallel projections.
  - 14. A system in accordance with claim 12 wherein said system comprises a detector having a plurality of parallel rows of detector elements configured to acquire projection data, and an x-ray source configured to project an x-ray beam, including an iso-ray, towards the detector through an object being scanned;
15. A system in accordance with claim 14 wherein to reconstruct a set of images of the object from the set of parallel projections, said system is configured to interpolate pairs of regions defined by the region boundaries to produce projections at a plane of reconstruction (POR).
16. A system in accordance with claim 15 wherein to reconstruct a set of images of the object from the set of parallel projections, said system is configured to apply a weighting function determined as a continuous function of a projection angle β
- to the projections at a plane of reconstruction for each image slice to be reconstructed.
17. A system in accordance with claim 16 wherein said system is configured to helically scan the object at a helical pitch greater than 6:
- 1.
18. A system in accordance with claim 17 wherein said system is configured to helically scan the object at a helical pitch of 8:
- 1.
19. A system in accordance with claim 18 wherein said system being configured to helically scan an object to acquire projection data comprises said system being configured to acquire projection data representing four image slices, and wherein said system being configured to reconstruct a set of images of the object from the set of parallel projections comprises said system being configured to reconstruct four images.
20. A system in accordance with claim 15 wherein said system being configured to helically scan an object comprises said system being configured to acguire projection data representing four image slices;
- andwherein said system being configured to apply a weighting function determined as a continuous function of a projection angle β
  
  to the projections at a plane of reconstruction for each image slice to be reconstructed comprises said system being configured to apply weighting functions written as;
  
  $\begin{matrix} w_{1} (β, γ) = {\begin{matrix} \frac{β - β_{4 -}^{'}}{β_{1}^{'} - β_{4 -}^{'}} & β_{4 -}^{'} \leq β < β_{1}^{'} \\ \frac{β - β_{2}^{'}}{β_{1}^{'} - β_{2}^{'}} & β_{1}^{'} \leq β < β_{2}^{'} \\ 0 & otherwise \end{matrix} \\ w_{2} (β, γ) = {\begin{matrix} \frac{β - β_{1}^{'}}{β_{2}^{'} - β_{1}^{'}} & β_{1}^{'} \leq β < β_{2}^{'} \\ \frac{β - β_{3}^{'}}{β_{2}^{'} - β_{3}^{'}} & β_{2}^{'} \leq β < β_{3}^{'} \\ 0 & otherwise \end{matrix} \\ w_{3} (β, γ) = {\begin{matrix} \frac{β - β_{2}^{'}}{β_{3}^{'} - β_{2}^{'}} & β_{2}^{'} \leq β < β_{3}^{'} \\ \frac{β - β_{4}^{'}}{β_{3}^{'} - β_{4}^{'}} & β_{3}^{'} \leq β < β_{4}^{'} \\ 0 & otherwise \end{matrix} \\ w_{4} (β, γ) = {\begin{matrix} \frac{β - β_{3}^{'}}{β_{4}^{'} - β_{3}^{'}} & β_{3}^{'} \leq β < β_{4}^{'} \\ \frac{β - β_{1 +}^{'}}{β_{4}^{'} - β_{1 +}^{'}} & β_{4}^{'} \leq β < β_{1 +}^{'} \\ 0 & otherwise \end{matrix} \end{matrix}$ where;
  
  w_i(β
  
  ,γ
  
  ) is a projection weighting function applied to a detector row i;
  
  γ
  
  is a detector angle;
  
  β
  
  _iis a projection angle at which an iso-ray of detector row i crosses a plane of reconstruction;
  
  β
  
  ′
  
  _i=β
  
  _i−
  
  γ
  
  is an angle of a parallel ray sample corresponding to a projection angle β
  
  _iof that sample; and
  
  β
  
  ′
  
  _i+=β
  
  ′
  
  _i+π and
  
  β
  
  ′
  
  _i−=β
  
  ′
  
  _i−
  
  π
  
  .
21. A system in accordance with claim 20 wherein said system is configured to scan the object at a helical pitch greater than 6:
- 1.
22. A system in accordance with claim 21 wherein said system is configured to scan the object at a helical pitch of 8:
- 1.

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Current Assignee
GE Medical Systems Global Technology Company LLC (GE Healthcare Technologies, Inc.)
Original Assignee
GE Medical Systems Global Technology Company LLC (GE Healthcare Technologies, Inc.)
Inventors
Hsieh, Jiang
Primary Examiner(s)
BRUCE, DAVID VERNON

Application Number

US09/639,368
Time in Patent Office

623 Days
Field of Search

378/4, 378/15, 378/901
US Class Current

378/15
CPC Class Codes

A61B 6/027   characterised by the use of...

A61B 6/032   Transmission computed tomog...

Y10S 378/901   Computer tomography program...

High pitch reconstruction of multislice CT scans

First Claim

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High pitch reconstruction of multislice CT scans

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