Optimal slices outside brain for fMRI acquisition

1

Hello experts,

The fMRI scans coming from our scanner are pretty tight on the z-axis which I assume is controlled by the number of slices in the scanning parameters. Here is an example fMRI scan:
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We also also acquire two spin echo images with the PE polarity reversed. These images are also tight on the brain along the z axis:

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Is there any disadvantage to having such a tight box along the z-axis for preprocessing? I thought I remember reading somewhere it may effect spatial distortion correction, but am unsure. I have run the data through fmriprep and I saw no major problems.

2

It should not affect the spatial distortion correction. The main disadvantage is if the subject moves too much and then the top of the head ends up outside of the Field of View. If you don’t particularly care about signal in the cerebellum, I would recommend you move the slices up a bit and collect a couple of slices outside of the brain, to account for potential motion.