Table 3. Optimal kVp/mA associated with optimal SDs, EDs, and CNRs of CT images were obtained by scanning 1, 5, and 10-year-old anthropomorphic phantom (AP) heads (Please refer to Table 1).

	kVp	mA	EDs (mSv)	SDs (HU)	CNRs
1-year-old	80	80	0.31	12.81	1.20
	100	40	0.34	12.49	1.72
	120	40	0.61	10.76	1.95
5-year-old	80	120	0.34	13.09	1.02
	100	80	0.52	11.79	1.50
	120	40	0.48	12.77	1.69
10-year-old	80	150	0.31	12.26	1.11
	100	80	0.37	11.04	1.65
	120	40	0.34	12.30	1.90

SD = standard deviation; CNR = contrast-to-noise ratio; ED = effective dose.