Please see the accompanying figure for typical sphere locations. Note that between each sector of cold rods there is a hole designated for the sphere stems to pass through. The holes for the sphere stems are located half way between the center of the phantom and the phantom wall. In the figure-right below, the red arrows point to the cold area occupied by the sphere stems in a reconstructed SPECT image. The order in which the spheres are arranged (largest to smallest, clock-wise versus anti-clock-wise, etc.) is not important. It is also not necessarily important that the largest sphere be located next to the largest sector of rods. For phantoms other than the one shown, please refer to photos or diagrams in the manual shipped with your phantom, or see the brochures for it on this web site.