Abstract: An image is produced of a target region from tomographic measurements through statistical inversion. The target region is mapped with a grid of voxels. Unknowns in the voxels are the components of a vector-valued variable. A next version of the vector-valued variable is repeatedly generated by drawing for each component a value from a conditional distribution. Elements of a theory matrix indicate, what is the contribution of each voxel in the grid to a detection result. The non-zero elements of the theory matrix are stored in a compressed form. A proper subset of the elements of the theory matrix is decompressed for either updating the quantity Ax and/or calculating the quantity AjT(Ax), where A is the theory matrix, x is the vector-valued variable and AjT is the transpose of the j:th column of the theory matrix.

Abstract: A method is provided for constructing a tomographic reconstruction through the application of statistical inversion. Unknowns associated with points of a reconstruction grid are represented with components of a vector-valued variable. A next version of the vector-valued variable is repeatedly created by drawing for each component a value from a conditional distribution. The components of a so generated version of the vector-valued variable are used as the tomographic reconstruction. The components are divided into sets, so that components in a set represent unknowns associated with mutually independent points of the reconstruction grid, or into independent collections. For at least two components of a set or at least two collections, the drawing of values from a conditional distribution is performed in parallel in a computer-implemented process.

Abstract: An image is produced of a target region from tomographic measurements through statistical inversion. The target region is mapped with a grid of voxels. Unknowns in the voxels are the components of a vector-valued variable. A next version of the vector-valued variable is repeatedly generated by drawing for each component a value from a conditional distribution. Elements of a theory matrix indicate, what is the contribution of each voxel in the grid to a detection result. The non-zero elements of the theory matrix are stored in a compressed form. A proper subset of the elements of the theory matrix is decompressed for either updating the quantity Ax and/or calculating the quantity AjT(Ax), where A is the theory matrix, x is the vector-valued variable and AjT is the transpose of the j:th column of the theory matrix.