quality assurance device for calibrating and testing the accuracy of movement - correlated computed tomography target - locating systems has a test unit sub - assembly adapted to be combined with a dynamic phantom system . the test unit sub - assembly has an axially and rotationally moveable test rod slideably disposed inside of a substantially hollow fixed housing . a matrix of markers , or “ fiducials ”, are located in the wall of the housing . a single fiducial is located near the distal end of the moveable test rod . the distal end portion of the moveable test rod is adapted to be connected to a motion actuator , which is programmed to oscillate the test rod in a predetermined pattern . when the test unit sub - assembly is inserted into a tissue equivalent phantom member , the combined sub - assembly and phantom member can then be subjected to four - dimensional imaging to generate a visual image . a visual comparison actual relative positions of the fiducials to the know positions of the fiducials in time indicates the accuracy of the 4d ct system .