TABLE III.

Fitting parameters (α, β) and root mean square from the residual for k factor for each CT examination category. The fitting parameters (α, β), RMSE, and the mean value for k factor for the body CT examination categories in bold and for the neurological categories in italic are shown here.

	k factor
Protocol	Alpha	Beta	RMSEa	Meanb
Head	−0.02	−6.25	0.0013	0.0011 ± 0.0001
Head-and-neck	−0.04	−4.65	0.0004	0.0028 ± 0.0004
Neck	−0.05	−3.98	0.0006	0.0044 ± 0.0007
Chest	−0.04	−2.52	0.0014	0.0211 ± 0.0028
Liver	−0.05	−2.57	0.0018	0.0195 ± 0.0035
Liver-to-kidney	−0.05	−2.37	0.0014	0.0187 ± 0.0037
Abdomen	−0.05	−2.49	0.0013	0.0177 ± 0.0034
Adrenal	−0.06	−1.98	0.0016	0.0212 ± 0.0047
Kidney	−0.07	−2.10	0.0018	0.0174 ± 0.0044
CAP	−0.05	−2.56	0.0007	0.0157 ± 0.0025
Abdomen-pelvis	−0.05	−2.64	0.0009	0.0144 ± 0.0026
Kidney-to-bladder	−0.07	−2.35	0.0017	0.0135 ± 0.0033
Pelvis	−0.06	−2.86	0.0009	0.0101 ± 0.0020

^aRoot-mean-square of the residuals (RMSE) represents the average discrepancy between the k factor values predicted by using the fitting function and the k factor values calculated from the organ dose values of individual patients. It has the same unit as k factor or effective dose.

^bMean represents the average value of the k factor calculated for individual patients. It has the same unit as k factor or effective dose.