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Table 2: Mean (SD) dose estimates and objective image-quality measures by age group and scanner
Younger Than 1.5 yr 1.5–6 yr 7–12 yr Older Than 13 yr
FBP IMR FBP IMR FBP IMR FBP IMR
CTDI_vol 29.9 (5.5) 21.8 (0.1) 30.6 (5.5) 22.8 (0.0) 31.5 (6.2) 27.5 (0.0)^{^a} 33.3 (6.9) 29.2 (0.6)^{^a}
SNR_THAL 9.3 (2.3) 22.0 (5.3) 8.6 (1.8) 20.2 (3.9) 8.8 (2.3) 18.7 (3.2) 8.6 (2.2) 17.9 (3.5)
SNR_WM 8.3 (2.3) 16.5 (3.8) 8.2 (2.3) 15.8 (3.3) 7.8 (1.3) 16.9 (4.3) 7.9 (2.4) 14.9 (2.9)
CNR 2.1 (0.9) 4.9 (1.3) 2.1 (1.1) 4.4 (0.9) 2.0 (1.0) 3.7 (0.9) 1.8 (0.6) 3.6 (1.0)
Note:—THAL indicates thalamus; WM, white matter; vol, volume.
↵a P value < .003. For all other results, P value < .001, equal variances t test.

	Younger Than 1.5 yr		1.5–6 yr		7–12 yr		Older Than 13 yr
	FBP	IMR	FBP	IMR	FBP	IMR	FBP	IMR
CTDI_vol	29.9 (5.5)	21.8 (0.1)	30.6 (5.5)	22.8 (0.0)	31.5 (6.2)	27.5 (0.0)^{^a}	33.3 (6.9)	29.2 (0.6)^{^a}
SNR_THAL	9.3 (2.3)	22.0 (5.3)	8.6 (1.8)	20.2 (3.9)	8.8 (2.3)	18.7 (3.2)	8.6 (2.2)	17.9 (3.5)
SNR_WM	8.3 (2.3)	16.5 (3.8)	8.2 (2.3)	15.8 (3.3)	7.8 (1.3)	16.9 (4.3)	7.9 (2.4)	14.9 (2.9)
CNR	2.1 (0.9)	4.9 (1.3)	2.1 (1.1)	4.4 (0.9)	2.0 (1.0)	3.7 (0.9)	1.8 (0.6)	3.6 (1.0)