This investigation presents the design and fabrication of a magnetic resonance imaging (MRI) test phantom for determining slice thickness, slice adjacency, slice offset, and slice angulation. This test phantom is a three-dimensional conic section of MRI image producing material; proper orientation allows analysis in each of the major imaging planes. The phantom design (geometrical configuration) incorporates both theoretical and quantitative methodologies. The necessary mathematical analyses are both simple and rapid. In addition, this phantom has been successfully used to assess the image slice parameters for computed tomography (CT) scanners and single photon emission computed tomography (SPECT) imaging systems. Slice profile parameter results, full width at half maximum (FWHM), from this phantom design are compared with conventional methods.