Extension of truncated CT images for use with emission tomography in multimodality medical images

A method for extending the effective FOV of a CT scanner, comprising the steps of:

• a) defining a projection data mask for CT transmission data to be acquired as CT projection data;
• b) defining a reconstruction mask for acquired CT projection data surrounding a FOV of said CT scanner to be used in calculating image reconstruction data;
• and
• c) performing a reconstruction data calculation using said CT projection data defined by said projection data mask and said reconstruction mask to obtain image reconstruction data for reconstruction of a CT image,
• wherein the calculation uses the image mask and an image center as one boundary, and
• wherein said iterative reconstruction data calculation comprises solving an equation in the form of:
• λ
• n
• +
• 1
• =
• λ
• n
• ⁢
• m
• ⁢
• 1
• B
• ⁢
• ⁢
• P
• ⁡
• (
• N
• )
• ⁢
• B
• ⁢
• ⁢
• P
• ⁡
• (
• y
• F
• ⁢
• ⁢
• P
• ⁡
• (
• λ
• n
• )
• )
• +
• λ
• 0
• ⁡
• (
• 1
• -
• m
• )
• for n=0 to a finite number of iterations, and where
• λn+1 is the calculated estimate of the image,
• λn is the previously calculated estimate of the image,
• λ0 is the original CT image,
• m is the image mask,
• N is the normalized projection data mask,
• y is the measured projection data,
• BP is the back projection operator, and
• FP is the forward projection operator.