TABLE 1.

Characteristics of Cranium by Age (36), X-Ray Generation Parameters, by Age, for Posterior-Anterior (PA) and Lateral (LAT) Projections, and Fitted Regression Parameters for Depth-Dose Functions, by Age and Projection

Phantom age (years):	<1		1		5		10		15		Adult
Cranium thickness (mm):	0.12		0.18		0.33		0.41		0.45		0.53
Cranium density (gm/cm3):	1.65		1.66		1.70		1.75		1.80		1.85
Projection:	PA	LAT	PA	LAT	PA	LAT	PA	LAT	PA	LAT	PA	LAT
X-ray generation parameters: Tube potential (kV), 1 mm aluminum + X mm copper
Tube potential (kV)	67	67	67	67	67	67	70	70	72	72	72	72
Filtration (mm copper)	0.3	0.6	0.3	0.6	0.3	0.6	0.2	0.3	0.2	0.3	0.2	0.3
Mean energy (keV)	46.6	50.4	46.6	50.4	46.6	50.4	45.8	47.9	46.6	48.8	46.6	48.8
Equivalent HVL (mm aluminum)	5	6.3	5	6.3	5	6.3	4.4	5.2	4.6	5.8	4.6	5.8
Regression fitted parameters for depth-dose functions
a1	0.871	0.900	0.818	0.857	0.694	0.754	0.596	0.643	0.570	0.618	0.513	0.563
a2	0.206	0.183	0.204	0.183	0.200	0.181	0.207	0.195	0.203	0.192	0.200	0.190
a3	−0.045	−0.045	−0.043	−0.043	−0.036	−0.038	−0.031	−0.033	−0.029	−0.031	−0.026	−0.028
a4	0.033	0.027	0.033	0.027	0.032	0.027	0.033	0.030	0.032	0.029	0.031	0.028