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Hi Yendiki, Anastasia,

Thank you very much for your reply! I have two more question.
(1)Even in the MNI space, the path positions of each subject could not be exactly coincident. So,how to identify the common midpoint for all subjects?
(2)how to identify step size of the equally sized step you mentioned above?

Thanks!
Qianwen

------------------ 原始邮件 ------------------
发件人: "Yendiki, Anastasia"<AYENDIKI@mgh.harvard.edu>;
发送时间: 2018年9月13日(星期四) 晚上11:44
收件人: "Freesurfer support list"<freesurfer@nmr.mgh.harvard.edu>;
主题: Re: [Freesurfer]回复： questions about trac-all -stat

Hi Qianwen,

(1) & (2): The native space coordinates along the path of all subjects (which are in their path stats files) are mapped to MNI space simply to identify a common midpoint for all subjects. This midpoint is mapped back to native space, and the FA/MD/etc. values for each subject are sampled along the path by stepping out by equally sized steps from the midpoint towards both ends. At each step, you get one row of the group table.

(3): Look for the paragraph "This text file contains various diffusion measures…” in the tutorial:
http://surfer.nmr.mgh.harvard.edu/fswiki/FsTutorial/TraculaStatistics
And slide “Path stats (values along the path)” in the course slides:
http://surfer.nmr.mgh.harvard.edu/pub/docs/tracula,fs.ppt

Hope this helps,
a.y

From: <freesurfer-bounces@nmr.mgh.harvard.edu> on behalf of 薛倩雯 <627611631@qq.com>
Reply-To: Freesurfer support list <freesurfer@nmr.mgh.harvard.edu>
Date: Wednesday, September 12, 2018 at 9:47 PM
To: Freesurfer support list <freesurfer@nmr.mgh.harvard.edu>
Subject: [Freesurfer] 回复： questions about trac-all -stat

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Hi Yendiki, Anastasia,
I am very sorry that I did not make myself clear. I mean I want to know how trac-all –stat does it.

(1)how to determine the first position and last position of all subjects' pathways when converting all pathstats.byvoxel.txt files to a table for group analyses?
In the tabel , The first position and last position of all subjects' pathways are determined by the longest pathway.

(2)how to complete correspondence of  points between subjects?
In the course slides, it said"Correspondence of points between subjects based on Euclidean distance in MNI space".This sentence is so vague that I can't understand it.

(3)what is values in table for group analyses,diffusion measure of center or something else?

I am very sorry that my question is a bit more, but I still hope that you can answer my doubts. Thanks!

Qianwen



------------------ 原始邮件 ------------------
发件人: "Yendiki, Anastasia"<AYENDIKI@mgh.harvard.edu>;
发送时间: 2018年9月12日(星期三) 晚上10:40
收件人: "Freesurfer support list"<freesurfer@nmr.mgh.harvard.edu>;
主题: Re: [Freesurfer] questions about trac-all -stat

Hi Qianwen – You don’t have to do (1) and (2), trac-all –stat does that for you. For a description of the measures, see the tutorial:
and the course slides:

Best,

a.y



From: <freesurfer-bounces@nmr.mgh.harvard.edu> on behalf of 薛倩雯 <627611631@qq.com>
Reply-To: Freesurfer support list <freesurfer@nmr.mgh.harvard.edu>
Date: Wednesday, September 12, 2018 at 1:13 AM
To: freesurfer <freesurfer@nmr.mgh.harvard.edu>
Subject: [Freesurfer] questions about trac-all -stat

        External Email - Use Caution      

Dear experts,
I have some questions about along-path analysis:
(1)how to determine the first position and last position of all subjects' pathway when converting all pathstats.byvoxel.txt files to a table for group analyses?

(2)how to complete correspondence of  points between subjects?

(3)what is values in table for group analyses,diffusion measure of center or something else?

Thanks!
Qianwen