Three-dimensional x-ray CT calibration and verification apparatus and method

An apparatus for calibrating an x-ray computed tomography device, the apparatus comprising:

• a plurality of objects formed from a material that is visible to x-rays, the plurality of objects being configured to receive x-rays without changing shape, each of the plurality of objects having substantially the same shape, the objects each having an object attenuation value to x-rays, each of the plurality of objects having a center point and being symmetrically shaped relative to its center point;
• and
• a base at least in part fixedly supporting the plurality of objects so that each of the plurality of objects contacts at least one of the other objects, the base having a base attenuation value to x-rays,
• the object attenuation value being greater than the base attenuation value,
• the center points of the plurality of objects together forming a three-dimensional volume,
• the plurality of objects being kinematically locked together.

A method of calibrating or verifying the dimensional accuracy of an x-ray computed tomography machine, the method comprising:

• providing an x-ray computed tomography machine having calibration settings;
• using the x-ray computed tomography machine to image a gauge to produce a gauge reconstruction, the gauge comprising first, second, and third spheres visible to x-rays, each sphere in contact with at least one other sphere, the first, second and third spheres being kinematically locked together, the centers of the first and second spheres forming a first line, the centers of the first and third spheres forming a second line, the first line diverging from the second line;
• measuring, in the gauge reconstruction, the distance between at least two of the spheres to produce measured center distance values;
• comparing the measured center distance values against known center distance values;
• and
• using the comparison to determine if there is a distance error in the gauge reconstruction.