Ji Jessica,
that's pretty low contrast. I would also bet that it's low bandwidth and
hence you have big temporal lobe B0 distortions that will change with
subject positioning. Are you stuck with this data going forward, or can you
change the acquisition parameters? If not, I think you will hav
Hi Jessica
the problem may be data quality! At 1.5T with a volume coil we would
typically get 2 scans to average. A TR of 14 is pretty short and will
reduce the SNR, and a TE of 6 is quite long and will reduce contrast. Can
you send us a tif of one slice to look at?
Bruce
On Thu, 28 Jul 201
Hi Martin,
When I did longitudinal analyses in the past, the output was very strange
even though I think I did everything correctly. If it's not too much
trouble for you, could you please take a look at my data and tell me what
I've done wrong? Since the files are so large, how would I send over
Hi Jessica,
I'd recommend to run the -base and the -long on these and see what
happens. If you then still see these differences, maybe we can take a
look at your data to figure out what causes this. It could be that the
WM segmentation fails somewhere. Anyway, the longitudinal stream should
help f
Hi Bruce,
Well for one of the subjects, the total temporal lobe volume from the first
scan was 149937 mm3, and the second scan's total temporal lobe volume was
183121 mm3. These numbers were found by summing the volumes from the
entorhinal, fusiform, parahippocampal, temporal pole, transverse tem
how are you computing the 20% difference? We definitely don't see this, and
Martin has done extensive testing of repeatability.
Bruce
On Wed, 27 Jul 2011, Jessica Liu
wrote:
Hi Martin,
Thanks for getting back to me. Actually I have two young controls who have 20%
differences between two s
Hi Martin,
Thanks for getting back to me. Actually I have two young controls who have
20% differences between two scans a day apart. Visually, there are not
abnormalities for the surfaces and hippocampus in both subjects i.e. on
tkmedit, the color of the hippocampus area (yellow) looks alright t
Hi Jessica,
I don't think this is normal. Is this a single subject? Of course in a
single subject lots of stuff can go wrong. Are the surfaces correct? And
the hippo label? Are there motion artifacts in the image etc.
Anyway, you should process this with the longitudinal stream:
http://freesurfer
Hi,
We found 20% differences in temporal lobe brain volume and ca. 5% difference
in the hippocampus volume between two data sets of a young normal volunteer
scanned 2 days apart.
We use the one-step 19 hours recon-all -all procedure and directly sum
select values taken from the lh.aparc.stats, rh
