On Fri, 24 Jun 2011, Jessica Liu wrote:
Hi Dr. Fischl,
Thanks for your comments. The aim of my study is to analyze the brain
volume in AD subjects. Most of the study was scanned on the 1.5T
(single-channel head coil) with a few subjects rescanned on the 3T
(12-channel head coil), so we would like to compare the brain volume of the
same subject on both scanners. In addition, the protocols on the two
scanners didn't match exactly due to the limitations of our over
15-years-old 1.5T scanner (i.e. non-isotropic voxel size). From your
comment, I gather that the 1.5T data is rather imprecise/unreliable. Since
I'm a summer student, do you recommend that I should concentrate on
analyzing the 3T data only, and hopefully all of the subjects can be
rescanned on the 3T? Thanks!
Jessica Liu
2011/6/23 Bruce Fischl <fischl@nmr.mgh.harvard.edu>
Hi Jessica,
the 1.5t scan looks kind of washed out and low contrast, but of
course it's hard to tell from an image. The 3T looks much
crisper. Were the sequence parameters matched? I'm not sure what
you're trying to show with this. The 3T multi-channel scan will
have a much, much higher SNR than the 1.5T single channel, so
the results will not at all be comparable.
Bruce
On Thu, 23 Jun 2011, Jessica Liu wrote:
Looking at the scans (attached, 3T on the left and 1.5T on
the right, yellow
hippocampus), I think you've made a good point. More
comments are much
appreciated, thanks!
Jessica Liu
2011/6/23 Pedro Paulo de Magalhães Oliveira Junior
<ppj@netfilter.com.br>
This is not normal. Maybe you should check the aseg
volume for
improper segmentation.
On Thu, Jun 23, 2011 at 19:27, Jessica Liu
<jessicaliu92@gmail.com>
wrote:
Hi everyone!
I'm currently a summer student working at a lab which uses
Freesurfer to measure hippocampal volumes. I noticed that
scanning the same patient first on a GE 3T (Multi-channel
head
coil) and then a GE 1.5T (single-channel head coil) 24
hours
later resulted in a 30% increase in the left hippocampus
volume
and a 18% increase for the right hippocampus based on the
values
in aseg.stats. Can anyone please comment on this and
explain
the large discrepancies? Thanks!
Jessica Liu
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