Pedro,
Thanks for your reply.
By false negatives I mean a lack of detection of atrophic areas which I know are present in this AD cohort, namely the parietal convexities. I'm unable to visualise them with FS.
Finally, you've recommended me not to seed anything to recon-all which had been skull stripped. Is there any way of going around this? And what about data which had been previously bias corrected?
Thank you very much for all you help!
Best,
Joao
-----Original Message----- From: freesurfer-bounces@nmr.mgh.harvard.edu [mailto:freesurfer-bounces@nmr.mgh.harvard.edu]On Behalf Of Pedro Paulo de Magalhães Oliveira Junior Sent: 03 October 2008 21:25 To: Joao Pereira Cc: freesurfer@nmr.mgh.harvard.edu Subject: Re: [Freesurfer] Voxel resolution impact / skull stripping and biascorrection replacement
João,
Here is my opinion:
I have worked on resolutions distinct than 1mm3 isotropic and usually I have no problem. What do you mean by false negatives in your cohort study?
I think you should avoid seeding data with skull striped by other program to the pipeline.
Best Regards,
PPJ
2008/10/3 Joao Pereira jmsp2@wbic.cam.ac.uk
Hello,
I have a couple of questions on which I would like to have your opinion.
The first is the voxel resolution impact on cortical thickness sensitivity. I'm using 1.25 mm3 isotropic voxels, and I know that FS interpolates scans to 1mm - is it possible that the 1.25 mm resolution hinders cortical thickness measurements? I'm asking this because I'm analysing an AD cohort whose result seems full of false negatives (I'm in the process of inspecting the intermediate steps as well - I just wanted to check if resolution was a factor as well).
I would also like to know if it is possible (and advisable) to input already optimally skull stripped and bias corrected brains into the recon-all pipeline. If that is possible, I would assume that I need to bypass those steps, and I would like to know which arguments to use in recon-all in order to do so.
Thank you very much for all your help!
Best,
Joao Pereira
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-- ----------------------------------------------------------- Pedro Paulo de M. Oliveira Junior Diretor de Operações Netfilter & SpeedComm Telecom