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System and method for GPU-based 3D nonrigid registration

  • US 7,483,034 B2
  • Filed: 02/22/2005
  • Issued: 01/27/2009
  • Est. Priority Date: 02/25/2004
  • Status: Expired due to Fees
First Claim
Patent Images

1. A method of registering two images using a graphics processing unit, said method comprising the steps of:

  • providing a pair of images with a first image and a second image, wherein said images comprise a plurality of intensities corresponding to a domain of grid points in a 3-dimensional space;

    calculating a gradient of the second image;

    initializing a displacement field on the grid point domain of the pair of images, wherein said displacement field transforms said second image into said first image;

    generating textures for the first image, the second image, the gradient, and the displacement field, and loading said textures into the graphics processing unit;

    creating a pixel buffer and initializing it with the texture containing the displacement field; and

    updating the displacement field in a rendering pass performed by the graphics processing unit according to the equation
    uk+1=uk

    [(I1

    I
    2

    (Id+uk))∇

    I2

    (Id+uk)]+α

    Δ

    uk,wherein uk and uk+1 are the displacement field and updated displacement field, respectively, I1 is the first image, I2 is the second image, ∇

    I2 is the gradient, Id is the identity map, ∇

    uk is the Laplacian of the displacement field, α

    is a regularization parameter, and δ

    is the time step for one or more iterations,wherein the boundary conditions of the 3-dimensional displacement field are clamp-to-edge, and further comprising decomposing the 3-dimensional displacement field into a 2-dimensional displacement field and controlling said boundary conditions of the 2-D displacement field by imposing a 2D mask, wherein said mask is a precomputed vector comprising 7 coefficients (a,b,c,d,e,f,g) that multiply each term of the displacement field according to the equation,


    uk(x+1,y)+b×

    uk(x−

    1,y)+c×

    uk(x,y+1)+d×

    uk(x,y−

    1)+e×

    uk(r,s)+f×

    uk(t,u)+g×

    uk(x,y),wherein uk(x,y) is the 2D displacement field, (a,b,c,d,e,f) are either 0 or 1, wherein 0 indicates a displacement field value outside the boundary, and 1 a point inside the boundary, g can vary between −

    6 and 0 depending on the number of nearest neighbor interior points about (x,y).

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