Twice the same image at 1x1x1, then use mri_robust_template to register
and average them together
On 4/6/2021 8:10 AM, Ramesh Babu wrote:
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Dear Eugenio and Philipp,
Thank you very much for your suggestions. Could you please give more
input on "acquire the T1WI double and average it after coregistration,
this increases the SNR".
Should aquire twise the same sequence with 1x1x2 voxel dimension?
Thanks
Ramesh
On Fri, 2 Apr, 2021, 9:00 PM Iglesias Gonzalez, Juan E.,
<jiglesiasgonza...@mgh.harvard.edu
<mailto:jiglesiasgonza...@mgh.harvard.edu>> wrote:
That all sounds right, thanks a lot Philipp!
Juan Eugenio Iglesias
Senior research fellow
CMIC (UCL), MGH (HMS) and CSAIL (MIT)
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*Date: *Friday, April 2, 2021 at 03:51
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<mailto:freesurfer@nmr.mgh.harvard.edu>>, Umesh Rurdrapatna
<umes...@gmail.com <mailto:umes...@gmail.com>>
*Subject: *Re: [Freesurfer] 2mm thick image for hippocampal
segmentation.
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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
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<mailto:freesurfer-boun...@nmr.mgh.harvard.edu>> im Auftrag von
Ramesh Babu <mgrameshbabu2...@gmail.com
<mailto: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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