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Method of determining (a) symmetry line(s) in a radiation image

  • US 6,263,097 B1
  • Filed: 06/24/1998
  • Issued: 07/17/2001
  • Est. Priority Date: 07/04/1997
  • Status: Expired due to Term
First Claim
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1. Method of determining a symmetry line in at least one of a horizontal direction and a vertical direction in a radiation image that is represented by a matrix of digital pixel values, comprising the steps of:

  • (i) calculating, in case of horizontal directions a symmetry point for each column of the image, and, in case of vertical direction, a symmetry point for each row of said image; and

    (ii) interconnecting calculated symmetry points, wherein a symmetry point for column j or row j, respectively, is obtained by;

    (1) calculating for column j or row j, and for each pixel c at position i in column j or row j, symmetrical difference sum values S according to the formula;

    S

    (i=c,j)
    =

    k=1m

    (i)


    [g

    (c+k,j)
    -(g

    (c-k,j)
    ]
    2
    ,


    where c=T, . . . , M−

    T−

    1, g(i,j) is a gray value at position (i,j), T is an offset parameter, M is a number of rows or columns, respectively in the matrix, and m(i) equals to min (i, M−

    i−

    1), (2) normalizing S to obtain {overscore (S)}, and (3) determining a minimal value {overscore (S)}min of the values {overscore (S)} obtained for each pixel c, and denoting a value c for which {overscore (S)} is equal to {overscore (S)}min as the symmetry point of column j or row j, respectively.

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