The structure of the MRI system phantom was modeled after the phantom designed for the Alzheimer’s Disease Neuroimaging Initiative (ADNI) MRI core. The system phantom consists of a deionized-water filled spherical polycarbonate shell with a 200 mm inner diameter. The spherical diameter was chosen to mimic a human head and was designed to fit in most head coil assemblies. The spherical geometry was chosen to reduce susceptibility distortions as discussed in the modeling section. Inside the spherical shell is a framework consisting of 5 polyphenylene sulfide (PPS) plates rigidly connected with PPS rods . PPS was chosen since it is a high performance plastic with low water absorption, low thermal expansion, and good machinability. The plates support 57 fiducial spheres, a 14 element T1 array, a 14 element T2 array, a 14 element proton density arrays, a resolution inset, wedges for slice profiling. The plates, as shown below, contain the following structures

Plate 5: 5 fiducial spheres, serial numbers, phantom ID, T1 array (green)

Plate 4: 13 fiducial spheres, T2 array (red), resolution inset

Plate 3: 26 fiducial spheres, proton density array (yellow)

Plate 2: 13 fiducial spheres, slice profile wedges

Plate 1: 5 fiducial spheres (blue)

The fiducial spheres are 10.0 �0.1 mm inner diameters set on a 3 dimensional 40 �0.1 mm grid. The origin of the phantom is defined as the center of the central fiducial sphere as shown in Fig. 3. The orientation was chosen so that the plates are in the coronal plane with left, right superior, inferior marked on each plate. A set of eye decals is included on the phantom shell to allow easy recognition and placement of the phantom within the scanner. The phantom is placed in the same fashion as a patient laying supine on the imaging bed.