Use of Hilbert transforms to simplify image reconstruction in a spiral scan cone beam CT imaging system
First Claim
1. A method for performing three dimensional computerized tomographic imaging a region-of-interest (ROI) in an object using a cone beam source of radiation energy, comprising the steps of:
- defining a source scan path that encircles the ROI in the object and is traversed by the cone beam source;
using the cone beam source, fixed relative to an area detector with both source and as detector movably positioned relative to the object, for applying radiation energy towards the object from a plurality of source positions along the scan path as said source traverses the scan path, said applying causing said area detector to acquire a set of cone beam projection data corresponding to a respective portion of the object at each of said source positions;
applying a mask to each set of the acquired projection data so that data inside the boundaries of each mask form a corresponding plurality of masked data sets;
calculating image data along each of the line segments L formed in the masked cone beam projection data acquired at each of said source positions, said calculating step comprising performing a plurality of one-dimensional (1D) convolving operations of the masked projection data along a respective group of the line segments L, the 1D convolving operation for each group of the line segments L developing an additive contribution to a new projection image; and
3D backprojecting the new projection image into a 3D space, thereby reconstructing a 3D image of the ROI in the object.
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Abstract
A method and apparatus for three dimensional (3D) computerized tomography (CT) imaging wherein a reconstructed image is developed by calculating along line segments L formed in cone beam data. The endpoints of which are determined by a data combination mask. At source positions near the top and bottom of the ROI, the mask is divided into separate portions using a horizontal line, each having a set of line segments L formed therein. The reconstruction data is calculated by performing one-dimensional (1D) convolving operations of the data along the line segments L, the 1D convolving operation developing an additive contribution to a new projection image. Finally, the new projection image is backprojected into a 3D space, thereby reconstructing a 3D image of the ROI in the object.
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Citations
21 Claims
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1. A method for performing three dimensional computerized tomographic imaging a region-of-interest (ROI) in an object using a cone beam source of radiation energy, comprising the steps of:
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defining a source scan path that encircles the ROI in the object and is traversed by the cone beam source;
using the cone beam source, fixed relative to an area detector with both source and as detector movably positioned relative to the object, for applying radiation energy towards the object from a plurality of source positions along the scan path as said source traverses the scan path, said applying causing said area detector to acquire a set of cone beam projection data corresponding to a respective portion of the object at each of said source positions;
applying a mask to each set of the acquired projection data so that data inside the boundaries of each mask form a corresponding plurality of masked data sets;
calculating image data along each of the line segments L formed in the masked cone beam projection data acquired at each of said source positions, said calculating step comprising performing a plurality of one-dimensional (1D) convolving operations of the masked projection data along a respective group of the line segments L, the 1D convolving operation for each group of the line segments L developing an additive contribution to a new projection image; and
3D backprojecting the new projection image into a 3D space, thereby reconstructing a 3D image of the ROI in the object. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
(a) determining a first line (406) which is tangent to the scan path (404) and perpendicular to its longitudinal axis;
(b) determining a second line (410) which is parallel to the first line (406) and which passes through the source position (Si) which acquired the data being masked; and
(c) defining as point C0 that point where the second line intersects the plane (412) of the detector.
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15. A method for performing three dimensional computerized tomographic imaging near at least one of an upper or lower boundary of a region-of-interest (ROI) in an object using a cone beam source of radiation energy, comprising the steps of;
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defining a source scan path that encircles the ROI near one of the boundaries in the object and is traversed by the cone beam source;
using the cone beam source, fixed relative to an area detector with both source and detector movably positioned relative to the object, for applying radiation energy towards the object from a plurality of source positions along the scan path as said source traverses the scan path, said applying causing said area detector to acquire a set of cone beam projection data corresponding to a respective portion of the object at each of said source positions;
applying a mask to each set of the acquired projection data so that data inside each mask form a corresponding plurality of masked data sets;
dividing those masked data sets acquired near a boundary of the ROI into a plurality of different spatial regions, one or more of said regions including a set of line segments L formed in the masked data which have a consistent spatial orientation with respect to each other, but with the line segments L of one region having a different spatial orientation with respect to the line segments L of another region;
calculating image data along each of the line segments L formed in the masked cone beam projection data acquired at each of said source positions, said image data corresponding to an additive contribution to a new projection image; and
3D backprojecting the new projection image into a 3D space, thereby reconstructing a 3D image of the ROI in the object. - View Dependent Claims (16, 17)
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18. A method for performing three dimensional computerized tomographic imaging near a boundary of a region-of-interest (ROI) in an object using a cone beam source of radiation energy, comprising the steps of:
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defining a source scan path that encircles the ROI in the object and is traversed by the cone beam source;
using the cone beam source, fixed relative to an area detector with both source and detector movably positioned relative to the object, for applying radiation energy towards the object from a plurality of source positions along the scan path as said source traverses the scan path, said applying causing said area detector to acquire a set of cone beam projection data corresponding to a respective portion of the object at each of said source positions;
applying a mask to each set of the acquired projection data so that data inside the boundaries of each mask form a corresponding plurality of masked data sets;
dividing those masked data sets acquired near a boundary of the ROI into a plurality of different spatial regions, one or more of said regions including a set of line segments L formed in the masked data which have a consistent spatial orientation with respect to each other, but with the line segments L of one region having a different spatial orientation with respect to the line segments L of another region;
calculating image data along each of said line segments L for developing an additive contribution to a new projection image; and
3D backprojecting the new projection image into a 3D space, thereby accurately reconstructing a 3D image of the boundary of the ROI in the object.
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19. Apparatus for performing three dimensional computerized tomographic imaging near a boundary of a region-of-interest (ROI) in an object using a cone beam source of radiation energy, comprising:
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a source of cone beam radiation energy;
a manipulator for providing a source scanning trajectory as a scan path that encircles the ROI in the object and causes the source and detector to traverse the scan path;
means for causing the source to apply radiation energy towards the object from a plurality of source positions along the scan path as said source traverses the scan path, said area detector acquiring cone beam projection data corresponding to respective portions of the object at each of said source positions; and
an image reconstruction processor for, applying a mask to the cone beam projection data acquired at each of said source positions, dividing those masked data sets acquired near a boundary of the ROI into a plurality of different spatial regions, at least two of said regions each including a set of line segments L formed therein which have a consistent spatial direction relative to each other, wherein the spatial direction of the line segments L of one region are different from the spatial direction of the line segments L of another region;
calculating image data along each of said line segments L for developing an additive contribution to a new projection image; and
3D backprojecting the new projection image into a 3D space, thereby accurately reconstructing a 3D image of the boundary of the ROI in the object. - View Dependent Claims (20, 21)
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Specification