Based on previous posts, the advantage of using structural (T1-weighted)
image for co-registration and spatial-normalization as opposed to
normalizing functional images directly to the EPI template is that:
1. T1-weighted images have higher spatial resolution which should allow
better overlap with the corresponding structures in the template.
2. there is the issue of EPI distortion variability in subjects and
that of the template (which would be less of an issue in structurals).
My question is:
if the EPI images are prone to distortion, it is quite likely that the
functional image (EPI) and the structural image (T1-weighted) cannot be
matched by rigid-body transformation (realignment or co-registration)
alone. So, if the EPI cannot be well-matched with the structural, how much
of an advantage is it using the T1-weighted for unified segmentation after
co-registration? Has a comparison been published between the two methods?