Table 1. Measurement variation by structure.

Structure	Mean volume (ml)	CV s (intra-session)	CV t (total)	|CV t −CV s |	Two-sided P -value
Intra-session (CVs) and total variation (CVt) shown as standard deviations, expressed as percentages of the mean value for each subject (i.e., the coefficient of variation). Values are averaged over all three subjects. The P-values shown indicate the likelihood of obtaining the observed difference, or greater, between CVs and CVt, when in fact there is no underlying difference between them.
Hippocampus	8.9	2.77%	2.92%	0.16%	0.41
Lateral ventricles	10.1	1.58%	3.40%	1.82%	<0.0001
Amygdala	3.8	4.69%	5.21%	0.53%	0.12
Putamen	11.6	4.04%	3.92%	0.13%	0.68
Pallidum	3.2	5.25%	5.42%	0.17%	0.67
Caudate	7.4	1.54%	1.58%	0.04%	0.67
Thalamus	12.9	5.98%	6.06%	0.08%	0.88
Cerebral white matter	496.6	0.88%	0.87%	0.00%	0.96