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Hi,
I try to answer but Eugenio may also add comments. Several points that are
important:
- 1.5 Tesla and 1x1x1 mm3 are at the limit of what the algorithm can manage.
- Post-aquisition reslicing to a higher resolution does not really increase the
information content. Internally the algorithm works at a much higher
resolution, anyway.
- If possible, switch to 3 Tesla.
- If possible and this is a prospective study, add a coronal T2 image and use
the bi-channel option. See papers of Iglesias et al. on this.
- What you could also do on a 1.5 T is acquire the T1WI double and average it
after coregistration, this increases the SNR.
- Generally, isometric resolutions are good due to the symmetry, of course.
- Also on 1.5 T, you may go bit below 1 mm with good head immobilization, and a
longer scanning time. BRAVO in general is a good T1 option.
Best,
Philipp
________________________________
Von: freesurfer-boun...@nmr.mgh.harvard.edu
<freesurfer-boun...@nmr.mgh.harvard.edu> im Auftrag von Ramesh Babu
<mgrameshbabu2...@gmail.com>
Gesendet: Freitag, 2. April 2021 09:29
An: Freesurfer support list; Umesh Rurdrapatna
Betreff: Re: [Freesurfer] 2mm thick image for hippocampal segmentation.
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Dear experts,
Sorry for reposting. I am expecting some response from experts, so that I can
proceed with confidence.
For our project work, we are looking for hippocampal and its subfield volumes.
Using GE 1.5T scanner, we tried a 3D BRAVO sequence with 1x1x1 resolution,
256x256x160 dimension with 8* flip angle which produced images with a lot of
noise. Then we tried the same sequence with 1x1x2 resolution, and 256x256x80
FOV, which produced a clean image without noise. When we reformatted the
images, it produces 0.5x0.5x1 resolution with 512x512x172 dimension.
Is this sequence good for hippocampal volume estimation and subfield
segmentation (also for whole-brain VBM analysis)?
Could you please suggest to me a correct sequence, if need to be changed?
Regards
Ramesh
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