Patent ID: 7967507

Claim:
A dimensional reference system for image reconstruction in tomography, comprising: a dimensional reference apparatus having: a plurality of spheres, each sphere having an X-ray absorption property configured to permit reconstruction of the sphere in tomography, each sphere further having a centroid and a diameter; a spacer unit configured to substantially fixedly space apart each of said plurality of spheres from each other at a known distance; wherein, when reconstructed in tomography, the dimensional reference apparatus is configured to provide subvoxel length scales for three dimensions, wherein said length scales are provided based on either the known distances between the centroids of the plurality of spheres, or the diameters of the spheres; and a diameter calculation element configured to calculate the diameter of at least one of the plurality of spheres, wherein the diameter calculation element includes a second moment tensor element configured to determine the second moment tensor of the at least one of the plurality of spheres.