A three-dimensional resolution gauge for evaluating performance of a tomographic imaging system includes a series of groupings of 3-dimensional line pairs. All of the line pairs are oriented at a common set acute angle relative to a reference x-y imaging plane. The frequency of the line pairs of respective groupings of the series vary from highest density to lowest density corresponding to fine resolution and coarse resolution, respectively. Imaging of the series of groupings 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.