Table 1.

The effect of different volume obscuring methods on results of selected skull stripping and gain field correction methods for sixteen evaluated MR head volumes. Notations: NMI - normalized mutual information; APD - average pixel distance. Statistical test p values indicate probability that the null hypothesis (i.e. the method for this column is not statistically different from the normalized filtering) is true

Applied processing	Similarity measure	Localized blur		Fill coating		Normalized filtering
		Mean	Statistical test	Mean	Statistical test	Mean
Original volume	NMI between the original and masked volumes	0.075	paired t, p = 5e-8	0.074	paired t, p = 4e-8	0.076
	APD between the original and masked volumes	11.1	paired t, p = 2e-6	14.3	paired t, p = 2e-8	9.2
Skull stripping	Volume overlap between the skull-stripped original and masked volumes	99.2 %	Wilcoxon signed rank, p = 4e-4	99.2 %	Wilcoxon signed rank, p = 3e-3	99.4 %
MR gain field correction	APD between the corrected original and masked volumes	0.42	Wilcoxon signed rank, p = 0.04	0.37	Wilcoxon signed rank, p = 0.09	0.33