In a method and apparatus for establishing the position of one or more constituent elements of a phantom in an image quality test for a medical imaging apparatus, an image of the phantom is obtained, and a landmark pixel or region of the image determined. Values of a given variable at pixels or regions at a predetermined distance from the landmark pixel or region are determined. The landmark pixel or region and the values of the variable are then used to establish the position of one or more of the constituent elements of the phantom.