Improving the accuracy and consistency of clinical target volume delineation for rectal cancer by an education program

Table 1 Definitions and formulas of the indices used for comparison

	Indices	Definition	Formula
Indices for geometric comparison analysis	Dice similarity coefficient index	Intersection of Vstu and Vref divided by their average	2 (Vstu ∩ Vref)/(Vstu + Vref)
	Inclusiveness index	Intersection of Vstu and Vref divided by Vstu	(Vref ∩ Vstu)/Vstu
	Concordance index	Intersection of Vstu and Vref divided by their union	(Vref ∩ Vstu)/(Vref ∪ Vstu)
	Relative volume difference	Difference between Vstu and Vref divided by Vref and multiplied by 100	(Vstu-Vref)/Vref × 100
Indices for interobserver variation	Maximum volume ratio	Ratio of the maximum volume to minimum volume contoured by the participants	Vmax/Vmin
	Coefficient of variation	Standard deviation of the volumes contoured by the participants multiplied by 100 and divided by the mean value	SD × 100/mean

V_stu: Target volume delineated by the participants; V_ref: Standard target volume delineated by the expert; V_max: Maximum volume contoured by the participants; V_min: Minimum volume contoured by the participants; SD: Standard deviation.