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.