TABLE 4

Comparison of Performance Characteristics in microPET Scanners

Performance characteristic		Focus 120 (this study)	Focus 120 (Laforest et al.)^*	R4^†	Focus 220^‡
Energy resolution (%)		18.3	N/A	23	18.5
Volumetric resolution (μL)^§	Center	1.92	2.87	5.1	2.5^¶
	1-cm radial offset	6.41	N/A	15.6	N/A
	2-cm radial offset	8.14	8.23	∼19^‖	6.3^¶
Absolute sensitivity for point source at center (%)	250∼750 keV, 10 ns	7.0	7.1	N/A	3.4
	250∼750 keV, 6 ns	6.7	6.7^**	4.37	3.0
	350∼650 keV, 10 ns	4.0	4.7^**	N/A	N/A
	350∼650 keV, 6 ns	3.8	4.4^**	2.45	2.1
Scatter fraction (%)^††	Mouse phantom	15.9	12.3	32.0	19.0
		(3-cm Ø, 7-cm L)	(2.5-cm Ø, 7-cm L)	(4.3-cm Ø, 7.6-cm L)	(3-cm Ø, 7-cm L)
	Rat phantom	35.0	26.3	38.0	36.4
		(6-cm Ø, 15-cm L)	(5-cm Ø, 15-cm L)	(6-cm Ø, 9.6-cm L)	(6-cm Ø, 15-cm L)
Peak NECR (kcps)^††	Mouse phantom	869 at 160.58 MBq	809 at 88.8 MBq	174 at 76.96 MBq	645 at 146.52 MBq
		(4.34 mCi)	(2.4 mCi)	(2.08 mCi)	(3.96 mCi)
		(3-cm Ø, 7-cm L)	(2.5-cm Ø, 7-cm L)	(4.3-cm Ø, 7.6-cm L)	(3-cm Ø, 7-cm L)
	Rat phantom	228 at 122.84 MBq	300 at 149.85 MBq	94 at 59.94 MBq	177 at 143.19 MBq
		(3.32 mCi)	(4.05 mCi)	(1.62 mCi)	(3.87 mCi)
		(6-cm Ø, 15-cm L)	(5-cm Ø, 15-cm L)	(6-cm Ø, 9.6-cm L)	(6-cm Ø, 15-cm L)

↵* Data published by Laforest et al. (13).
↵† Data published by Knoess et al. (19).
↵‡ Data published by Tai et al. (12).
↵§ Data were not corrected for source dimension, positron range, or acolinearity of positron annihilation and were estimated from nonoversampled axial profiles except for Focus 220.
↵¶ Axial resolution was estimated from oversampled axial profiles (Tai et al.) (12).
↵‖ Estimated from Figure 5 in Knoess et al. (19).
↵** Estimated from Figure 1 in Laforest et al. (13).
↵†† Data were measured using same energy window (250–750 keV) and coincidence window (6 ns) but the phantom sizes (Ø, diameter; L, length) were not identical.
N/A = not available.