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Method and apparatus for producing a three-dimensional computerized tomography image of an object with improved conversion of cone beam data to radon data

  • US 5,341,460 A
  • Filed: 09/13/1993
  • Issued: 08/23/1994
  • Est. Priority Date: 08/28/1992
  • Status: Expired due to Term
First Claim
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1. A method of imaging comprising the steps of:

  • (a) using a computed tomography cone beam source to apply cone beam energy, dependent upon an object of interest, to an area detector;

    (b) detecting the cone beam energy to define a cone beam data image X(i,j) based upon the cone beam energy detected at points (i,j) on the area detector, each point (i,j) having a corresponding detector element;

    (c) determining the value of line integral J on the detector where ##EQU7## and where X(t) is cone beam data image at point t along a line of integration, SC'"'"' is the distance from a source S of cone beam energy to a rotation center C'"'"' on the detector, SC is the distance from the source S to a point C, wherein point C is the closest point to the origin on the line of integration and Δ

    C is the displacement of C'"'"' from C, the value of J being determined by the substeps of;

    (c1) calculating a modified image F(i,j)=X(i,j)/R(i,j) where R(i,j) is the distance from source S to point (i,j) on the area detector;

    (c2) calculating a two-dimensional Fourier transform g(m,n) in (m,n) space using a fast Fourier transform and dependent on F(i,j);

    (c3) interpolating from g(m,n) a line of Fourier components g.sub.α

    (k) where α

    is a desired projection angle, k are inputs to g.sub.α

    along the line of Fourier components passing through an origin in (m,n) space and oriented perpendicular to the desired projection angle;

    (c4) performing a one-dimensional fast Fourier transform on g.sub.α

    (k) to obtain a one-dimensional projection p.sub.α

    (1);

    (c5) obtaining p.sub.α

    (s) by one-dimensional interpolation from p.sub.α

    (1) where p.sub.α

    (s) is a line integral on a particular line at a location s in the desired projection angle α

    ;

    (d) using a Radon inversion process on p.sub.α

    (s) to produce a reconstructed three-dimensional image of the object; and

    (e) displaying the reconstructed three-dimensional image of the object.

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