Abstract: A quality assurance test phantom having a shell wherein water and test objects reside in conjunction with a bellows capable of longitudinally translating one or more of a variety of test objects within the inside of the phantom via a screw mechanism is described. These test objects are employed in novel tests to quantitatively evaluate the imaging performance of a computed tomography ("CT") device with specific regard to the construction of pseudo-planar slices produced from scan data taken using helical scanning techniques.