Image quality and quantification accuracy dependence on patient body mass in (89)Zr PET/CT imaging

BACKGROUND: This study was conducted to clarify how patient body mass affects the image quality and quantification accuracy of images obtained using (89)Zr PET/CT. (89)Zr PET/CT images from time-of-flight (TOF) PET/CT and semiconductor (SC) PET/CT were obtained using three types (M, L, LL; corresponding to increasing patient body weight) of custom-made body phantoms designed similarly to the National Electrical Manufacturers Association (NEMA) IEC body phantom. The phantom data were analyzed visually and quantitatively to derive image quality metrics, namely detectability of the 10-mm-diameter hot sphere, percent contrast for the 10-mm-diameter hot sphere (Q(H,10 mm)), percent background variability (N(10mm)), contrast-to-noise ratio (Q(H,10 mm)/N(10mm)), and coefficient of variation of the background area (CV(BG)). RESULTS: Visual assessment revealed that all the 10-mm-diameter hot spheres of the three types of phantoms were identifiable on both SC and TOF PET/CT images. The N(10mm) and CV(BG) values were within the proposed reference levels, and decreased with acquisition duration for both PET/CT types. At 10-min acquisition, the Q(H,10 mm)/N(10mm) of SC PET/CT was greater than the proposed reference level in all phantoms. However, the Q(H,10 mm)/N(10mm) of TOF PET/CT was greater than the proposed reference level in M-type phantom alone. All the SUV(BG) values were within 1.00 ± 0.05 for both PET/CT types. CONCLUSIONS: This study showed that the image quality and quantification accuracy depend on the patient’s body mass, suggesting that acquisition time on (89)Zr PET/CT should be changed according to the patient’s body mass.