Table 3.

Assessment of Interobserver Variability. Cohen’s and Fleiss’ Kappa Coefficients are presented in Table 3 as an assessment of the interobserver variability of determining radiographic progression or response for each of the methods. The novel volumetric method had the strongest agreement among the two neuroradiologists (Cohen’s Kappa=0.96) and also had strong agreement (Fleiss’ Kappa=0.79) among all examiners. Cohen’s Kappa Statistic for Agreement among the two neuroradiologists for 2D and 1D were 0.54 and 0.46, respectively.

Neuroradiologist 1
		1D method				2D method				Volumetric method
		Complete Response/ Regression	Stable	Progression	Total	Complete Response/ Regression	Stable	Progression	Total	Complete Response/ Regression	Stable	Progression	Total
Neuroradiologist 2	Complete Response/ Regression	4	3	4	11	5	2	4	11	5	0	0	5
	Stable	2	17	1	20	1	15	2	18	0	18	0	18
	Progression	2	3	8	13	2	2	11	15	0	1	20	21
	Concordance	65.9% (29 of 44)				70.5% (31 of 44)				97.7% (43 of 44)
	Cohen’s Kappaa	0.46				0.54				0.96

Abbreviations: 1D, one-dimensional; 2D, two-dimensional.

^aInterobserver agreement on radiographic calls of examiners for the 1D, 2D, and volumetric methods.