Because scans were acquired at multiple sites, images were resampled to a standard voxel size.  All images were resampled to 1 mm isotropic using the c3d program.  Version c3d-nightly-MacOS-x86_64.dmg was downloaded online from https://sourceforge.net/projects/c3d/files/c3d/Nightly/c3d-nightly-MacOS-x86_64.dmg/download.