Table 1. Intrarater and interrater reliability for grayscale histogram analysis.

Relative reliability of the ROI selection method for grayscale histogram analysis is determined using intraclass correlation coefficients (ICC), and absolute reliability is expressed via the standard error of measurement (SEM). Both the Rectangular Marquee Tool and Free Hand Tool displayed comparable levels of reliability across image processing platforms and examiners, with the echogenicity estimates obtained with ImageJ software exhibiting slightly lower SEM values. Measurement values are in grayscale levels.

		Photoshop			ImageJ
		$\overline{X}\pm SD$	ICC (95% CI)a	SEM	$\overline{X}\pm SD$	ICC (95% CI)a	SEM
Examiner 1b	Rectangular Marquee Tool	28.09 ± 11.51	.993 (.982)	.96	27.72 ± 11.45	.996 (.990)	.72
	Free Hand Tool	27.52 ± 11.77	.992 (.978)	1.05	26.55 ± 11.38	.995 (.986)	.80
Examiner 2b	Rectangular Marquee Tool	28.19 ± 11.64	.993 (.982)	.97	27.69 ± 11.39	.996 (.990)	.72
	Free Hand Tool	27.35 ± 11.68	.992 (.978)	1.04	27.01 ± 11.63	.995 (.986)	.82
Both examinersc	Rectangular Marquee Tool	28.15 ± 11.57	.993 (.982)	.97	27.71 ± 11.42	.996 (.990)	.72
	Free Hand Tool	27.44 ± 11.72	.992 (.978)	1.05	26.78 ± 11.51	.995 (.986)	.81

Notes.

^aone-sided lower limit (CI = confidence interval).

^bICC_3,k used to determine intrarater reliability.

^cICC_2,k used to determine interrater reliability.

p < .001 for all ICC values.

(SEM, standard error of the measurement).