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 <fis...@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 <p...@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 <jessicali...@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 >> >> ______________________________**_________________ >> Freesurfer mailing list >> Freesurfer@nmr.mgh.harvard.edu >> https://mail.nmr.mgh.harvard.**edu/mailman/listinfo/**freesurfer<https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer> >> >> >> The information in this e-mail is intended only for the person >> to whom it is >> addressed. If you believe this e-mail was sent to you in error >> and the e-mail >> contains patient information, please contact the Partners >> Compliance HelpLine at >> http://www.partners.org/**complianceline<http://www.partners.org/complianceline>. >> If the e-mail was sent >> to you in error >> but does not contain patient information, please contact the >> sender and properly >> dispose of the e-mail. >> >> >> >> >>
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