3D image reconstruction for helical partial cone beam scanners using wedge beam transform
First Claim
1. A method of image reconstruction from wedge beam data comprising:
- (a) collecting cone beam data in two-dimensional arrays, said collected data corresponding to rays of penetrating radiation diverging in two dimensions from a common vertex as the vertex travels along a curve with each element of the data related to line integrals of an object being reconstructed taken along each ray;
(b) defining a local coordinate system having three mutually orthogonal axes and an origin at the vertex, wherein a third axis thereof extends in a direction tangential to the curve at the vertex;
(c) rebinning the collected data into a wedge beam format, wherein sets of parallel rays are grouped to define planes of radiation that angularly diverge from a common axis;
(d) computing a one-dimensional convolution of the rebinned data in the local coordinate system along a direction parallel to the third axis;
(e) weighting the convolved data; and
,(f) three-dimensionally backprojecting the weighted convolution.
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Abstract
A method of image reconstruction from wedge beam data includes collecting cone beam data in two-dimensional arrays. The collected data corresponds to rays of penetrating radiation diverging in two dimensions from a common vertex which travels along a curve. Each element of the data is related to line integrals of an object being reconstructed taken along each ray. A local coordinate system is defined having three mutually orthogonal axes and an origin at the vertex. The third axis of the local coordinate system extends in a direction tangential to the curve at the vertex. The collected data is rebinned into a wedge beam format wherein sets of parallel rays are grouped to define planes of radiation that angularly diverge from a common axis. A one-dimensional convolution of the rebinned data is computed in the local coordinate system along a direction parallel to the third axis. Finally, the convolved data is weighted and three-dimensionally backprojected. In a preferred embodiment, the curve defines a helical path, and the kernel for the one-dimensional convolution of the rebinned data is a ramp convolver.
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Citations
17 Claims
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1. A method of image reconstruction from wedge beam data comprising:
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(a) collecting cone beam data in two-dimensional arrays, said collected data corresponding to rays of penetrating radiation diverging in two dimensions from a common vertex as the vertex travels along a curve with each element of the data related to line integrals of an object being reconstructed taken along each ray; (b) defining a local coordinate system having three mutually orthogonal axes and an origin at the vertex, wherein a third axis thereof extends in a direction tangential to the curve at the vertex; (c) rebinning the collected data into a wedge beam format, wherein sets of parallel rays are grouped to define planes of radiation that angularly diverge from a common axis; (d) computing a one-dimensional convolution of the rebinned data in the local coordinate system along a direction parallel to the third axis; (e) weighting the convolved data; and
,(f) three-dimensionally backprojecting the weighted convolution. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A CT scanner comprising:
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a first gantry which defines an examination region; a rotating gantry mounted on the first gantry for rotation about the examination region; a source of penetrating radiation arranged on the rotating gantry for rotation therewith, said source of penetrating radiation emitting a cone-shaped beam of radiation that passes through the examination region as the rotating gantry rotates; a subject support which holds a subject being examined at least partially within the examination region, wherein at least one of the first gantry and the subject support is translated such that the subject passes through the examination region while the rotating gantry is rotated and the source of penetrating radiation follows a helical path relative to the subject; a two-dimensional array of radiation detectors arranged to receive the radiation emitted from the source of penetrating radiation after it has traversed the examination region; a reconstruction processor which reconstructs images of the subject from data collected by the two-dimensional array of radiation detectors, said reconstruction processor including; a rebinning processor which rebins the data into a wedge beam format such that sets of parallel rays of radiation are grouped to define planes of radiation that angularly diverge from a common axis which is tangential to the helical path; a convolver which takes the data from the rebinning processor and performs a one-dimensional convolution on it in a local coordinate system along a direction which is tangential to the helical path; a data processor which takes the data from the convolver and weights it; and
,a backprojector which takes the data from the data processor and three-dimensionally backprojects it into an image memory; and
,a human viewable display which accesses the image memory to display reconstructed images of the subject. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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Specification