When discussing resolution in the field of coordinate measuring technology, two categories must be fundamentally differentiated: structural (or spatial) resolution and positional (or metrological) resolution. The structural resolution defines how small structures on the measured object can be and still be detectable. It is substantially determined by the size of the focal spot (blurring) of the X- ray tubes. To achieve a high resolution, appropriately low values should be selected for the electrical power (the product of current and voltage at the tube). Deviations of the rotary axis from the ideal behavior (e.g. run out) also cause blurring in the reconstructed volume.  The same is true with deviations from the correct position of the rotary axis. This is typically on the line between the focal spot and the center of the sensor. Of course, the size of the pixels of the X-ray sensor also directly limits the spatial resolution. Any binning that is used and blurring due to the scintillator also have an effect. This resolution of the X-ray sensor causes an effect that is inversely proportional to the magnification in the object plane. Digital filtering is applied for subsequent data processing, such as the back projection for reconstruction. Convoluting the resolution functions of the individual components yields the effective resolution of the system. In practice, the structural resolution can be determined most simply by checking the measurability of the smallest test structures, such as spheres, cylinders, holes or arrangements of these.  The positional resolution, on the other hand, defines the smallest increment that can be practically used when measuring the position of a structure (thus it is also known as metrological resolution).  For tomography, this is the smallest increment when determining the position of a transition point between two materials, or between the material and the surrounding air. It is based on the structural resolution. When calculating the measurement points from the volume, the position of these points is determined at a higher resolution that is provided by the voxel size. This is possible because the grayscale value information of the voxels is also utilized (subvoxeling). The use of raster tomography, together with suitable magnifications, can provide an additional increase in the metrological resolution. In this case, the reproducibility of the mechanical axes and the resolution of the length measurement system also have an effect. The metrological resolution determines the reproducibility when measuring geometric features. Systematic measurement errors also play a role.

Seen in the image above: Factors that affect spatial resolution: a) The focal point dominates the resolution. b) The rotary axis dominates the resolution. c) The components are optimally tuned.