EJNMMI Research

Table 3 Repeatability metrics for [¹³N]ammonia one-tissue compartment (reversible) model parameters for grey matter and selected regions of interest (ROIs)

From: Evaluation of [ ¹³ N]ammonia positron emission tomography as a potential method for quantifying glutamine synthetase activity in the human brain

ROI	K₁ [n = 5] (mL/100 g/min)					k₂ [n = 5] (1/min)
	S1	S2	ICC	VAR	AbsVAR	S1	S2	ICC	VAR	AbsVAR
Grey Matter	20.1 ± 1.5	18.6 ± 1.3	− 0.83	− 8 ± 14	10 ± 12	0.0069 ± 0.0029	0.0074 ± 0.0022	0.58	11 ± 38	28 ± 24
White matter	14.5 ± 1.2	13.5 ± 0.8	− 0.89	− 7 ± 14	9 ± 11	0.0059 ± 0.0027	0.0064 ± 0.0021	0.57	12 ± 43	32 ± 27
Hippocampus_l	18.9 ± 2.4	17.6 ± 1.0	− 0.06	− 7 ± 14	10 ± 11	0.0122 ± 0.0061	0.0144 ± 0.0041	0.89	23 ± 27	25 ± 24
OL_ling_G_l	23.7 ± 3.0	21.5 ± 1.0	− 0.41	− 9 ± 15	10 ± 14	0.0072 ± 0.0023	0.0075 ± 0.0020	0.58	5 ± 30	24 ± 15
G_cing_post_l	22.2 ± 1.6	20.6 ± 1.3	− 0.68	− 7 ± 13	9 ± 11	0.0065 ± 0.0032	0.0075 ± 0.0019	0.58	19 ± 40	30 ± 31
Putamen_l	23.3 ± 1.9	21.1 ± 1.5	− 0.83	− 10 ± 15	12 ± 12	0.0063 ± 0.0028	0.0072 ± 0.0028	0.59	13 ± 44	34 ± 27
Thalamus_l	22.5 ± 2.1	20.7 ± 1.1	− 0.79	− 8 ± 15	10 ± 13	0.0089 ± 0.0030	0.0101 ± 0.0024	0.72	15 ± 23	24 ± 9
Cerebellum_l	22.4 ± 2.0	20.6 ± 1.3	− 0.69	− 8 ± 14	9 ± 13	0.0061 ± 0.0027	0.0072 ± 0.0022	0.61	19 ± 39	33 ± 25

The table presents the intraclass correlation coefficient (ICC), percent mean fractional difference (VAR) and percent absolute fractional difference (AbsVAR) across test (S1) and retest (S2) scans. Data are presented as mean ± standard deviation for grey matter, white matter and the left (l) hippocampus, lingual gyrus (OL_ling_G), posterior cingulate gyrus (G_cing_post), putamen, thalamus, and cerebellum

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