1. A three-dimensional resolution gauge for evaluating performance of a tomographic imaging system, comprising: a series of groupings of three-dimensional line pairs, all of the line pairs being oriented at a common set acute angle relative to a reference x-y imaging plane, frequency of the line pairs of respective groupings of the series varying from highest density to lowest density corresponding to fine resolution and coarse resolution, respectively, wherein imaging of the series of groupings of line pairs by the tomographic imaging system provides, in a single scan, a simultaneous visualization of combined effects of x-y in-plane resolution and slice thickness z direction resolution, wherein each grouping comprises repetitive structures located in spaced apart parallel planes all oriented at said common set acute angle relative to the reference x-y image plane, and wherein the repetitive structures comprises fins or ramps.