Comparison between PET/MR and PET/CT: NEMA tests and image quality

Abstract

OBJECTIVE The aim of this study was to explore differences in image quality between PET/MR and PET/CT hybrid imaging systems using standard quality control and National Electrical Manufacturers Association (NEMA) tests. METHODS Image acquisition and quality control tests were investigated according to the standards of NEMA NU 2-2007 using NEMA phantom and recommended image acquisition techniques. The phantom consists of lesion-like hot spheres of diameters 10, 13, 17, and 22 mm filled with 8:1 18F activity ratio to background. The remaining 28 and 37 mm cold spheres were filled with water only. A 700-mm linear line source was prepared with 3.08 mCi (140.6 MBq), and all essential ROIs were drawn after image acquisition to calculate contrast. RESULTS In PET/MR, the average contrast of 10, 13, 17, and 22 mm diameter hot spheres in the phantom was 56%, 72%, 78%, and 85%, respectively. While the contrast of 10, 13, 17, and 22 mm diameter hot spheres in PET/CT was 53%, 66%, 72%, and 79%, respectively. CONCLUSION PET/MR image contrast was higher than PET/CT by 9%.