Table 2.

Comparison between CFs calculated from acquisitions NEMA Cal.1 and NEMA Val. for comparable sphere–background activity ratios (SBARs)

Sphere volume (VOI volume) [cc]	Phantom NEMA Cal. 1 acquisition		Phantom NEMA Val. acquisition		CF difference error (%) between NEMA Cal 1. and NEMA Val.
Sphere volume (VOI volume) [cc]	CF [cps/MBq]	SBAR	CF [cps/MBq]	SBAR	CF difference error (%) between NEMA Cal 1. and NEMA Val.
26.52 (22.7 cc)	3.92	15.91	4.06	15.28	3.44
11.49 (10.3 cc)	3.19	15.91	2.96	15.28	7.21
5.71 (6.36 cc)	2.64	15.91	1.84	15.28	30.30

CF, Calibration factor; SBAR, Sphere-to-background counts/activity ratio