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Exact region of interest cone beam imaging without circle scans

  • US 6,333,960 B1
  • Filed: 06/30/1999
  • Issued: 12/25/2001
  • Est. Priority Date: 03/22/1999
  • Status: Expired due to Term
First Claim
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1. A method for performing three dimensional computerized tomographic imaging of a region-of-interest (ROI) in an object using a cone beam source of radiation energy, comprising the steps of:

  • defining a source scanning trajectory along a longitudinal axis as a 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 cone beam projection data corresponding to respective portions of the object at each of said source positions;

    masking the cone beam projection data acquired at each of said source positions with a mask having upper and lower boundaries formed by cone beam projections onto the plane of the detector of portions of the source scan path that are above and below, respectively, the source position that acquired the data being masked;

    calculating data for each of a plurality of line segments L formed in the masked cone beam projection data acquired at each of said source positions, said mask being used during said calculating step to divide said plurality of line segments L into separate groups, each group having a different technique for limiting the length of the line segments L therein; and

    reconstruction processing the data calculated for said line segments L having their length determined by the mask as defined above, for reconstructing a 3D image of the ROI in the object;

    wherein the calculating step includes a step for determining a point (C0) on an axial line crossing the mask which intersects a projection of the source position that acquired the data, the point Co is determined by;

    a) drawing a first line (606) which is tangent to the scan path (604) and perpendicular to its longitudinal axis;

    b) drawing a second line which is parallel to the first line, and which passes through the source position (Si) which acquired the data being masked; and

    c) defining as point Co, that point where the second line intersects the detector (612).

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