Methods and apparatus for cone beam artifact suppression in scanning imaging systems

• US 6,408,042 B1
• Filed: 06/15/2001
• Issued: 06/18/2002
• Est. Priority Date: 06/15/2001
• Status: Expired due to Term

• 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 V.
• Assistant Examiner(s): Hobden, Pamela R.
• Application Number:
  US09/882,160
• Time in Patent Office: 368 Days
• Field of Search: 378/4, 378/15, 378/19, 378/21, 378/901
• US Class Current: 378/4
• CPC Class Codes: A61B 6/027 characterised by the use of a particular data acquisition trajectory, e.g. helical or spiral
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

One embodiment is a method for reconstructing at least one image representative of an object utilizing a scanning imaging system having a multislice detector array and a radiation source. The method includes helically scanning the object with the scanning imaging system to acquire a plurality of projection views of the object, including projection views acquired at different cone angles of the radiation beam; selecting a region of reconstruction (ROR) to define sets of conjugate samples in the projection views; and reconstructing at least one image of the object. The reconstruction includes weighting the sets of conjugate samples using a cone-angle dependent weighting function, and filtering and backprojecting the weighted samples.

Claims

1. A method for reconstructing at least one image representative of an object with a scanning imaging system having a multislice detector array and a radiation source configured to emit a radiation beam through the object and towards the multislice detector array, the multislice detector array having a plurality of detector elements arranged in a plurality of detector rows, said method comprising:

helically scanning the object with the scanning imaging system to acquire a plurality of projection views of the object, including projection views acquired at different cone angles of the radiation beam;

selecting a region of reconstruction (ROR) to define sets of conjugate samples in the projection views; and

reconstructing at least one image of the object, said reconstruction including weighting the sets of conjugate samples using a cone-angle dependent weighting function, and filtering and backprojecting the weighted samples.

2. A method in accordance with claim 1 wherein said weighting the sets of conjugate samples includes applying a detector row k dependent scaling factor w_k that scales inversely to the cone angles.

3. A method in accordance with claim 2 wherein said selecting a region of reconstruction comprises selecting a straight line in a sonogram space, the straight line written as:

${\mathrm{\beta <br><br>}}_{0,k}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\frac{\left(9-2<br><br>k\right)<br><br>\mathrm{\pi <br><br>}}{5}-\mathrm{\alpha <br><br>\gamma <br><br>},$

where;

k is a row number 1, 2, . . . ;

β

is a projection angle;

γ

is a detector angle; and

α

is a slope adjustment parameter.

4. A method in accordance with claim 1 wherein said selecting an ROR comprises selecting a piecewise linear ROR.

5. A method in accordance with claim 1 wherein said selecting an ROR comprises selecting a nonlinear ROR.

6. A method for reconstructing at least one image representative of an object with a scanning imaging system having a multislice detector array and a radiation source configured to emit a radiation beam through the object and towards the multislice detector array, the multislice detector array having a plurality of detector elements arranged in a plurality of detector rows, said method comprising:

helically scanning the object with the scanning imaging system to acquire a plurality of projection views of the object, including projection views acquired at different cone angles of the radiation beam;

selecting a region of reconstruction (ROR) to define sets of conjugate samples in the projection views; and

reconstructing at least one image of the object, said reconstruction including weighting the sets of conjugate samples using a cone-angle dependent weighting function, and filtering and backprojecting the weighted samples;

said weighting the sets of conjugate samples includes applying a detector row k dependent scaling factor w_k that scales linearly and inversely with the cone angles.

7. A method in accordance with claim 6 wherein the scanning imaging system is a computed tomographic (CT) imaging system, the multislice detector array has eight detector rows, and wherein the cone-angle dependent weighting functions are written as:

$h_k<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\{\begin{array}{c}\frac{w_k<br><br>\left[\mathrm{\beta <br><br>}-{\mathrm{\beta <br><br>}}_{1,k}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\right]}{{\mathrm{\beta <br><br>}}_{0,k}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)-{\mathrm{\beta <br><br>}}_{1,k}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)},{\mathrm{\beta <br><br>}}_{1,k}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\le <br><br>\mathrm{\beta <br><br>}\le <br><br>{\mathrm{\beta <br><br>}}_{0,k}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\\ \frac{w_k<br><br>\left[{\mathrm{\beta <br><br>}}_{2,k}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)-\mathrm{\beta <br><br>}\right]}{{\mathrm{\beta <br><br>}}_{2,k}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)-{\mathrm{\beta <br><br>}}_{0,k}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)},{\mathrm{\beta <br><br>}}_{0,k}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\le <br><br>\mathrm{\beta <br><br>}\le <br><br>{\mathrm{\beta <br><br>}}_{2,k}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\\ 0,\mathrm{otherwise},\end{array}$

where;

k is a row number 1, 2, . . . ;

β

is a projection angle;

γ

is a detector angle;

α

is a slope adjustment parameter;

${\mathrm{\beta <br><br>}}_{0,k}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\frac{\left(9-2<br><br>k\right)<br><br>\mathrm{\pi <br><br>}}{5}-\mathrm{\alpha <br><br>\gamma <br><br>};<br><br>{\mathrm{\beta <br><br>}}_{1,k}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\frac{\left(8-2<br><br>k\right)<br><br>\mathrm{\pi <br><br>}}{5}+\left(\mathrm{\alpha <br><br>}-2\right)<br><br>\mathrm{\gamma <br><br>};<br><br>\mathrm{and}$${\mathrm{\beta <br><br>}}_{2,k}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\frac{\left(10-2<br><br>k\right)<br><br>\mathrm{\pi <br><br>}}{5}+\left(\mathrm{\alpha <br><br>}-2\right)<br><br>\mathrm{\gamma <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{for}<br><br>\text{\hspace{1em}<br><br>}<br><br>k=1,\mathrm{\dots <br><br>}<br><br>\text{\hspace{1em}<br><br>},8;<br><br>\mathrm{and}$$w_k=\{\begin{array}{cc}0.125,& k=1\\ 0.25,& k=2\\ 0.375,& k=3\\ 0.5,& k=4\\ 0.5,& k=5\\ 0.375,& k=6\\ 0.25,& k=7\\ 0.125,& k=8.\end{array}$

8. A method in accordance with claim 7 wherein said helical scanning of the object comprises scanning the object at a helical pitch of 5:

1.

9. A scanning imaging system for reconstructing at least one image representative of an object, said scanning imaging system comprising a multislice detector array, a radiation source configured to emit a radiation beam through an object to be imaged and towards said multislice detector array, said multislice detector array comprising a plurality of detector elements arranged in a plurality of detector rows, said scanning imaging system configured to:

helically scan the object to be imaged to acquire a plurality of projection views of the object, including projection views acquired at different cone angles of said radiation beam;

select a region of reconstruction (ROR) to define sets of conjugate samples in said projection views; and

reconstruct at least one image of the object, wherein to reconstruct said at least one image, said multislice imaging system is configured to weight said sets of conjugate samples using a cone-angle dependent weighting function, and to filter and backproject said weighted samples.

10. A scanning imaging system in accordance with claim 9 wherein to weight said sets of conjugate samples, said scanning imaging system is configured to apply a detector row k dependent scaling factor w_k that scales inversely to said cone angles.

11. A scanning imaging system in accordance with claim 10 wherein to select a region of reconstruction, said scanning imaging system is configured to select a straight line in a sonogram space, said straight line written as:

${\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\frac{\left(9-2<br><br>\text{\hspace{1em}<br><br>}<br><br>k\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\pi <br><br>}}{5}-\mathrm{\alpha <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\gamma <br><br>},$

where;

k is a row number 1, 2, . . . ;

β

is a projection angle;

γ

is a detector angle; and

α

is a slope adjustment parameter.

12. A scanning imaging system in accordance with claim 9 wherein to select an ROR, said scanning imaging system is configured to select a piecewise linear ROR.

13. A scanning imaging system in accordance with claim 9 wherein to select an ROR, said scanning imaging system is configured to select a nonlinear ROR.

14. A scanning imaging system for reconstructing at least one image representative of an object, said scanning imaging system comprising a multislice detector array, a radiation source configured to emit a radiation beam through an object to be imaged and towards said multislice detector array, said multislice detector array comprising a plurality of detector elements arranged in a plurality of detector rows, said scanning imaging system configured to:

helically scan the object to be imaged to acquire a plurality of projection views of the object, including projection views acquired at different cone angles of said radiation beam;

select a region of reconstruction (ROR) to define sets of conjugate samples in said projection views; and

reconstruct at least one image of the object, wherein to reconstruct said at least one image, said multislice imaging system is configured to weight said sets of conjugate samples using a cone-angle dependent weighting function, and to filter and backproject said weighted samples;

wherein to weight said sets of conjugate samples, said scanning imaging system is configured to apply a detector row k dependent scaling factor w_k that scales linearly and inversely with said cone angles.

15. A scanning imaging system in accordance with claim 14 wherein said scanning imaging system is a computed tomographic (CT) imaging system, said multislice detector array has eight detector rows, and wherein said cone-angle dependent weighting functions are written as:

$h_k<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\{\begin{array}{cc}\frac{w_k<br><br>\left[\mathrm{\beta <br><br>}-{\mathrm{\beta <br><br>}}_{1,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\right]}{{\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)-{\mathrm{\beta <br><br>}}_{1,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)},& {\mathrm{\beta <br><br>}}_{1,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\le <br><br>\mathrm{\beta <br><br>}\le <br><br>{\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\\ \frac{w_k<br><br>\left[{\mathrm{\beta <br><br>}}_{2,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)-\mathrm{\beta <br><br>}\right]}{{\mathrm{\beta <br><br>}}_{2,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)-{\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)},& {\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\le <br><br>\mathrm{\beta <br><br>}\le <br><br>{\mathrm{\beta <br><br>}}_{2,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\\ 0,& \mathrm{otherwise},\end{array}$

where;

k is a row number 1, 2, . . . ;

β

is a projection angle;

γ

is a detector angle;

α

is a slope adjustment parameter;

$\begin{array}{c}{\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\text{\hspace{1em}<br><br>}<br><br>\frac{\left(9-2<br><br>\text{\hspace{1em}<br><br>}<br><br>k\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\pi <br><br>}}{5}-\mathrm{\alpha <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\gamma <br><br>};<br><br>{\mathrm{\beta <br><br>}}_{1,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\frac{\left(8-2<br><br>\text{\hspace{1em}<br><br>}<br><br>k\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\pi <br><br>}}{5}+\left(\mathrm{\alpha <br><br>}-2\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\gamma <br><br>};<br><br>\mathrm{and}\\ {\mathrm{\beta <br><br>}}_{2,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\text{\hspace{1em}<br><br>}<br><br>\frac{\left(10-2<br><br>\text{\hspace{1em}<br><br>}<br><br>k\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\pi <br><br>}}{5}+\left(\mathrm{\alpha <br><br>}-2\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\gamma <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{for}<br><br>\text{\hspace{1em}<br><br>}<br><br>k=1,\mathrm{\dots <br><br>}<br><br>\text{\hspace{1em}<br><br>},8;<br><br>\mathrm{and}\\ w_k=\text{\hspace{1em}<br><br>}<br><br>\{\begin{array}{cc}0.125,& k=1\\ 0.25,& k=2\\ 0.375,& k=3\\ 0.5,& k=4\\ 0.5,& k=5\\ 0.375,& k=6\\ 0.25,& k=7\\ 0.125,& k=8.\end{array}\end{array}$

16. A scanning imaging system in accordance with claim 15 configured to helically scan the object at a helical pitch of 5:

1.

17. A processor for reconstructing at least one image representative of an object helically scanned by a scanning imaging system, said processor configured to:

input a plurality of projection views of a scanned object, including projection views acquired at different cone angles of a radiation beam by a multislice detector array having a plurality of detector rows;

select a region of reconstruction (ROR) to define sets of conjugate samples in said projection views; and

reconstruct at least one image of the object, wherein to reconstruct said at least one image, said processor is configured to weight said sets of conjugate samples using a cone-angle dependent weighting function, and to filter and backproject said weighted samples.

18. A processor in accordance with claim 17 wherein to weight said sets of conjugate samples, said processor is configured to apply a detector row k dependent scaling factor w_k that scales inversely to the cone angles.

19. A processor in accordance with claim 18 wherein to select a region of reconstruction, said processor is configured to select a straight line in a sonogram space, said straight line written as:

${\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\frac{\left(9-2<br><br>\text{\hspace{1em}<br><br>}<br><br>k\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\pi <br><br>}}{5}-\mathrm{\alpha <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\gamma <br><br>},$

where;

k is a row number 1, 2, . . . ;

β

is a projection angle;

γ

is a detector angle; and

α

is a slope adjustment parameter.

20. A processor in accordance with claim 17 wherein to select an ROR, said scanning imaging system is configured to select a piecewise linear ROR.

21. A processor in accordance with claim 17 wherein to select an ROR, said scanning imaging system is configured to select a nonlinear ROR.

22. A processor for reconstructing at least one image representative of an object helically scanned by a scanning imaging system, said processor configured to:

input a plurality of projection views of a scanned object, including projection views acquired at different cone angles of a radiation beam by a multislice detector array having a plurality of detector rows;

select a region of reconstruction (ROR) to define sets of conjugate samples in said projection views; and

reconstruct at least one image of the object, wherein to reconstruct said at least one image, said processor is configured to weight said sets of conjugate samples using a cone-angle dependent weighting function, and to filter and backproject said weighted samples;

wherein to weight said sets of conjugate samples, said processor is configured to apply a detector row k dependent scaling factor w_k that scales linearly and inversely with the cone angles.

23. A processor in accordance with claim 22 wherein said cone-angle dependent weighting functions are written as:

$h_k<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\{\begin{array}{cc}\frac{w_k<br><br>\left[\mathrm{\beta <br><br>}-{\mathrm{\beta <br><br>}}_{1,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\right]}{{\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)-{\mathrm{\beta <br><br>}}_{1,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)},& {\mathrm{\beta <br><br>}}_{1,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\le <br><br>\mathrm{\beta <br><br>}\le <br><br>{\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\\ \frac{w_k<br><br>\left[{\mathrm{\beta <br><br>}}_{2,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)-\mathrm{\beta <br><br>}\right]}{{\mathrm{\beta <br><br>}}_{2,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)-{\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)},& {\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\le <br><br>\mathrm{\beta <br><br>}\le <br><br>{\mathrm{\beta <br><br>}}_{2,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\\ 0,& \mathrm{otherwise},\end{array}$

where;

k is a row number 1, 2, . . . ;

β

is a projection angle;

γ

is a detector angle;

α

is a slope adjustment parameter;

$\begin{array}{c}{\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\text{\hspace{1em}<br><br>}<br><br>\frac{\left(9-2<br><br>\text{\hspace{1em}<br><br>}<br><br>k\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\pi <br><br>}}{5}-\mathrm{\alpha <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\gamma <br><br>};<br><br>{\mathrm{\beta <br><br>}}_{1,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\frac{\left(8-2<br><br>\text{\hspace{1em}<br><br>}<br><br>k\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\pi <br><br>}}{5}+\left(\mathrm{\alpha <br><br>}-2\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\gamma <br><br>};<br><br>\mathrm{and}\\ {\mathrm{\beta <br><br>}}_{2,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\text{\hspace{1em}<br><br>}<br><br>\frac{\left(10-2<br><br>\text{\hspace{1em}<br><br>}<br><br>k\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\pi <br><br>}}{5}+\left(\mathrm{\alpha <br><br>}-2\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\gamma <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{for}<br><br>\text{\hspace{1em}<br><br>}<br><br>k=1,\mathrm{\dots <br><br>}<br><br>\text{\hspace{1em}<br><br>},8;<br><br>\mathrm{and}\\ w_k=\text{\hspace{1em}<br><br>}<br><br>\{\begin{array}{cc}0.125,& k=1\\ 0.25,& k=2\\ 0.375,& k=3\\ 0.5,& k=4\\ 0.5,& k=5\\ 0.375,& k=6\\ 0.25,& k=7\\ 0.125,& k=8.\end{array}\end{array}$

24. A processor in accordance with claim 23 configured to input a plurality of projection views scanned at a helical pitch of 5:

1.

25. A computer-readable medium having encoded thereon instructions interpretable by a computer to instruct the computer to:

input a plurality of projection views of a scanned object, including projection views acquired at different cone angles of a radiation beam by a multislice detector array having a plurality of detector rows;

select a region of reconstruction (ROR) to define sets of conjugate samples in said projection views; and

reconstruct at least one image of the object, wherein to reconstruct said at least one image, said processor is configured to weight said sets of conjugate samples using a cone-angle dependent weighting function, and to filter and backproject said weighted samples.

26. A computer-readable medium in accordance with claim 25 wherein to instruct the computer to weight said sets of conjugate samples, said computer-readable medium has encoded thereon instructions configured to instruct the computer to apply a detector row k dependent scaling factor w_k that scales inversely to the cone angles.

27. A computer-readable medium in accordance with claim 25 wherein to instruct the computer to select a region of reconstruction, said computer-readable medium has encoded thereon instructions configured to instruct the computer to select a straight line in a sonogram space, said straight line written as:

${\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\frac{\left(9-2<br><br>\text{\hspace{1em}<br><br>}<br><br>k\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\pi <br><br>}}{5}-\mathrm{\alpha <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\gamma <br><br>},$

where;

k is a row number 1, 2, . . . ;

β

is a projection angle;

γ

is a detector angle; and

α

is a slope adjustment parameter.

28. A computer-readable medium in accordance with claim 25 wherein instruct the computer to select an ROR, said computer-readable medium has encoded thereon instructions configured to instruct the computer to select a piecewise linear ROR.

29. A computer-readable medium in accordance with claim 25 wherein to instruct the computer to select an ROR, said computer-readable medium has encoded thereon instructions configured to instruct the computer to select a nonlinear ROR.

30. A computer-readable medium having encoded thereon instructions interpretable by a computer to instruct the computer to:

input a plurality of projection views of a scanned object, including projection views acquired at different cone angles of a radiation beam by a multislice detector array having a plurality of detector rows;

select a region of reconstruction (ROR) to define sets of conjugate samples in said projection views; and

reconstruct at least one image of the object, wherein to reconstruct said at least one image, said processor is configured to weight said sets of conjugate samples using a cone-angle dependent weighting function, and to filter and backproject said weighted samples;

wherein to instruct the computer to weight said sets of conjugate samples, said computer-readable medium has encoded thereon instructions configured to instruct the computer to apply a detector row k dependent scaling factor w_k that scales linearly and inversely with the cone angles.

31. A computer readable medium in accordance with claim 30 wherein said cone-angle dependent weighting functions are written as:

$h_k<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\{\begin{array}{cc}\frac{w_k<br><br>\left[\mathrm{\beta <br><br>}-{\mathrm{\beta <br><br>}}_{1,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\right]}{{\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)-{\mathrm{\beta <br><br>}}_{1,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)},& {\mathrm{\beta <br><br>}}_{1,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\le <br><br>\mathrm{\beta <br><br>}\le <br><br>{\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\\ \frac{w_k<br><br>\left[{\mathrm{\beta <br><br>}}_{2,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)-\mathrm{\beta <br><br>}\right]}{{\mathrm{\beta <br><br>}}_{2,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)-{\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)},& {\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\le <br><br>\mathrm{\beta <br><br>}\le <br><br>{\mathrm{\beta <br><br>}}_{2,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)\\ 0,& \mathrm{otherwise},\end{array}$

where;

k is a row number 1, 2, . . . ;

β

is a projection angle;

γ

is a detector angle;

α

is a slope adjustment parameter;

$\begin{array}{c}{\mathrm{\beta <br><br>}}_{0,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\text{\hspace{1em}<br><br>}<br><br>\frac{\left(9-2<br><br>\text{\hspace{1em}<br><br>}<br><br>k\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\pi <br><br>}}{5}-\mathrm{\alpha <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\gamma <br><br>};<br><br>{\mathrm{\beta <br><br>}}_{1,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\frac{\left(8-2<br><br>\text{\hspace{1em}<br><br>}<br><br>k\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\pi <br><br>}}{5}+\left(\mathrm{\alpha <br><br>}-2\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\gamma <br><br>};<br><br>\mathrm{and}\\ {\mathrm{\beta <br><br>}}_{2,k}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{\gamma <br><br>},\mathrm{\beta <br><br>}\right)=\text{\hspace{1em}<br><br>}<br><br>\frac{\left(10-2<br><br>\text{\hspace{1em}<br><br>}<br><br>k\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\pi <br><br>}}{5}+\left(\mathrm{\alpha <br><br>}-2\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\gamma <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{for}<br><br>\text{\hspace{1em}<br><br>}<br><br>k=1,\mathrm{\dots <br><br>}<br><br>\text{\hspace{1em}<br><br>},8;<br><br>\mathrm{and}\\ w_k=\text{\hspace{1em}<br><br>}<br><br>\{\begin{array}{cc}0.125,& k=1\\ 0.25,& k=2\\ 0.375,& k=3\\ 0.5,& k=4\\ 0.5,& k=5\\ 0.375,& k=6\\ 0.25,& k=7\\ 0.125,& k=8.\end{array}\end{array}$

32. A computer-readable medium in accordance with claim 31 having encoded thereon instructions configured to instruct the computer to input a plurality of projection views scanned at a helical pitch of 5:

1.