A simulation-based assessment of the revised NEMA NU-2 70 cm long test phantom for PET

A 70 cm long polyethylene cylinder of radius 10 cm containing an off-center line source has been suggested for the characterization of PET tomograph whole-body performance in terms of scatter fraction, sensitivity to randoms and count-rate capability. In this work we perform a series of Monte Carlo simulations of a full-ring BGO system operating in 3D mode and a full-ring sodium iodide system operating in 3D mode to determine how closely scatter fraction and NEC results from the 70 cm cylinder follow those found in anthropomorphic activity and attenuation distributions. We find that the 70 cm cylinder measurements correctly rank-order the tomographs in terms of scatter fraction and NEC performance, but do not always accurately predict the actual scatter fractions or the peak NEC values encountered in the anthropomorphic models. Peak NEC for the phantom occurs at around double the activity concentrations which give rise to peak NEC in the anthropomorphic objects.