Image reconstructing apparatus and image reconstructing method
When a group of (pre-processed) projection data is stored into a projection-data storage unit, a Gaussian-based expansion-data creating unit creates a group of Gaussian-based expansion data that is expanded from each of the group of projection data through linear combination based on a plurality of Gaussian functions that is stored by a Gaussian-function storage unit and has different center points. A reconstruction-image creating unit then creates a reconstruction image by using the Gaussian-based expansion-data created by the Gaussian-based expansion-data creating unit, and stores the created reconstruction image into an image storage unit.
1. An image reconstructing apparatus comprising:
a Gaussian-based expansion-data group creating unit that creates a group of Gaussian-based expansion data that is expanded from each of a group of projection data through linear combination based on a plurality of Gaussian functions having different center points uniformly distributed at positional coordinates; and
a reconstruction-image creating unit that creates a reconstruction image by performing one of two sequences of processing sequentially on each of the group of the Gaussian-based expansion data created by the Gaussian-based expansion-data group creating unit, the two sequences of processing including a sequence of Fourier transform processing, one-dimensional inverse-Fourier transform processing, and back projection processing, and a sequence of Fourier transform processing and two-dimensional inverse-Fourier transform processing, wherein
the reconstruction-image creating unit executes Fourier transform on each of the group of the Gaussian-based expansion-data by calculating a simple sum of product directly using a corresponding expansion coefficient that is calculated when expanding each of the group of projection data by a corresponding one of the Gaussian functions and thereby statistical noises are removed from the projection data while high-frequency components corresponding to profile information about internal structures are left substantially intact without executing a low-pass filter processing.
2. The image reconstructing apparatus according to claim 1 , wherein the Gaussian-based expansion-data group creating unit creates the group of the Gaussian-based expansion data by acquiring a group of one-dimensional Gaussian functions to be a base for expanding each of the group of the projection data with respect to a cross section orthogonal to a projection direction in a plurality of two-dimensional Gaussian functions that is uniformly arranged in a field of view of the reconstruction image and has different center points.
3. An image reconstructing apparatus comprising:
a reconstruction-image creating unit that calculates two-dimensional Gaussian-expansion coefficients to be a base for expanding a group of projection data by a plurality of two-dimensional Gaussian functions that is uniformly arranged in a field of view of a reconstruction image and has different center points distributed at positional coordinates, thereby creating a reconstruction image processed from the group of the projection data through back projection processing, wherein statistical noises are removed from the projection data while high-frequency components corresponding to profile information about internal structures are left substantially intact without executing a low-pass filter processing.
4. An image reconstructing method comprising:
creating by a Gaussian-based expansion-data group creating unit a group of Gaussian-based expansion data that is expanded from each of a group of projection data through linear combination based on a plurality of Gaussian functions having different center points uniformly distributed at positional coordinates; and
creating by a reconstruction-image creating unit a reconstruction image by sequentially performing one of two sequences of processing on each of the group of the Gaussian-based expansion data created by the Gaussian-based expansion-data group creating unit, the two sequences of processing including a sequence of Fourier transform processing, one-dimensional inverse-Fourier transform processing, and back projection processing, and a sequence of Fourier transform processing and two-dimensional inverse-Fourier transform processing, wherein
the reconstruction-image creating unit executes Fourier transform on each of the group of the Gaussian-based expansion-data by calculating a simple sum of product directly using a corresponding expansion coefficient that is calculated when expanding each of the group of projection data by a corresponding one of the Gaussian functions wherein statistical noises are removed from the projection data while high-frequency components corresponding to profile information about internal structures are left substantially intact without executing a low-pass filter processing.
5. An image reconstructing method comprising:
creating by a reconstruction-image creating unit a reconstruction image processed from a group of projection data through back projection processing by calculating two-dimensional Gaussian-expansion coefficients to be a base for expanding the group of the projection data by a plurality of two-dimensional Gaussian functions that is uniformly arranged in a field of view of a reconstruction image and has different center points distributed at positional coordinates wherein statistical noises are removed from the projection data while high-frequency components corresponding to profile information about internal structures are left substantially intact without executing a low-pass filter processing.