Fig 3.

The use of a standardized image acquisition protocol improves statistical power for detection of brain volume changes in multicenter imaging studies. The plot shows that the number of subjects required per group is less for a given effect size when using a standardized protocol (orange lines) compared to a nonstandardized protocol (green lines). As an example, to detect a 50,000 mm³ volume change (~5%) requires approximately 60 subjects for a standardized protocol and approximately 90 subjects for a nonstandardized protocol.