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ITERATIVE KERNEL ARTIFACT DECONVOLUTION

IP.com Disclosure Number: IPCOM000238489D
Publication Date: 2014-Aug-28
Document File: 14 page(s) / 2M

Publishing Venue

The IP.com Prior Art Database

Abstract

The invention includes a post processing technique to reduce cone-beam and other artifacts in computer tomography (CT) reconstructions. The technique includes computing artifact kernel coefficient such that artifacts in the original image are defined and are subtracted. As a result, the artifacts in the image are reduced. The technique is based on the knowledge of structure in the image, which results into artifacts and on the nature, which include shape, and magnitude of the artifact patterns. Primary application of the technique is to reduce artifact, which results due to missing frequencies. These are due to nature of the axial CT scanning geometry and become more severe as the distance from the center plane increases. Another application is in limited view angle artifacts. Missing views also result in the absence of same particular azimuthal frequencies and utilize similar correction technique, compute the artifact pattern, identify the artifact causing objects, and determine the coefficients of the kernel to explain coefficient efficiently. Another application includes longitudinal z truncation, trans axial (xy-) truncation or interior tomography and metal artifacts as hollow projection. All application results in limited angle data for certain regions in the image and applies same correction technique.

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ITERATIVE KERNEL ARTIFACT DECONVOLUTION

 

BRIEF ABSTRACT

The invention includes a post processing technique to reduce cone-beam and other artifacts in computer tomography (CT) reconstructions. The technique includes computing artifact kernel coefficient such that artifacts in the original image are defined and are subtracted. As a result, the artifacts in the image are reduced. The technique is based on the knowledge of structure in the image, which results into artifacts and on the nature, which include shape, and magnitude of the artifact patterns. Primary application of the technique is to reduce artifact, which results due to missing frequencies. These are due to nature of the axial CT scanning geometry and become more severe as the distance from the center plane increases.  Another application is in limited view angle artifacts. Missing views also result in the absence of same particular azimuthal frequencies and utilize similar correction technique, compute the artifact pattern, identify the artifact causing objects, and determine the coefficients of the kernel to explain coefficient efficiently.  Another application includes longitudinal z truncation, trans axial (xy-) truncation or interior tomography and metal artifacts as hollow projection. All application results in limited angle data for certain regions in the image and applies same correction technique.

KEYWORDS

Artifact, Computer tomography, coefficient, Missing frequency


DETAILED DESCRIPTION

Third generation cone beam CT faces challenge in term of cone-beam artifacts, particularly in case of axial or circular scan trajectories. Three-root causes of these artifacts are Z-truncation, Mishandled data and missing frequency.

Z-truncation includes some voxel always to be in the x-ray beam but some other voxels sometimes are inside and outside of the x-ray beam.  There is interest to reconstruct the largest possible volume based on a provided irradiation profile, which are not only 360 degrees region but also at least the entire 180-degree region.

            Any provided voxel are visible by a source and detector for a certain angular view range. Some radon direction or frequencies are measured twice and reconstruction requires to correctly acquiring into account redundancy. Simple sonogram domain weighting does not always acquire goal redundancy and results mishandled data. Inside 360-degree region, a circular scan results in some missing frequencies along the Z-direction. The amount of missing frequencies increase with distance from the mid plane, which is the x-ray focal spot moves.

            A conventional technique includes an additional scan data from a helical trajectory.

 

            Another conventional technique includes cartoonizing object and simulating the artifact, which is resulted by cartoonizing object.

            Yet another technique includes a forward model of the acquisition process and iteratively minimizes diffe...