[Mristudio-users] ImgVal Calculation

[Jun Yi Wang]

Hi Dr. Mori,

I have a question to your response.  The fiber density (fiber count/voxel) is usually more than 1, so many line propagations or fibers will go through the same voxels.  When DTI Studio calculates mean FA for a reconstructed fiber tract, does it calculate based on all voxels in the fiber tract with each voxel appear once or based on fibers so that voxels belong to multiple fibers will be appear multiple times?

Thanks,
Jun Yi



________________________________
From: susumu <susumu at mri.jhu.edu>
To: "DTI Studio, ROI Editor, Landmarker Questions/Support" <mristudio-users at mristudio.org>
Sent: Wednesday, December 3, 2008 3:36:46 PM
Subject: Re: [Mristudio-users] ImgVal Calculation


This is an interesting observation. It should be a simple binary masking. The pixel with fibers are 1 and other pixels are 0. We multiply this masking to loaded images and calculate average and STD. Do you think our values are off? If so, this is definitely something we should look into. Could you send us (not by MailingList) one fiber file and a co-registered FA map?
 

________________________________

From:mristudio-users-bounces at mristudio.org [mailto:mristudio-users-bounces at mristudio.org] On Behalf Of Hui Jing Yu
Sent: Friday, November 21, 2008 1:56 PM
To: mristudio-users at mristudio.org
Subject: [Mristudio-users] ImgVal Calculation
 
Dear DTI Studio users,
 
I have a question regarding the ImgVal calculation under statistical profile for fiber tracking.  I got very different mean FA values (differences ranging from 0.04 to 0.1)  when I tried these two methods (keeping all parameters consistent and same version of DTI):
1.       Load previously saved fiber track (binary) into DTI studio, click on fiber statistics and I have  for Mean of ImgVal and Std. of ImgVal
2.       Using MATLAB, apply the same binary fiber track onto FA image (analyze format), calculate mean/std values for all the pixels/voxels belonging to this fiber track
How are these mean ImgVal calculated?  I assume it is just a mean values for all the pixels/voxels that are contained in the fiber track of interest.
 
Thanks in advance for your help.
 
HJ


      
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.mristudio.org/pipermail/mristudio-users/attachments/20081203/df736ed0/attachment.html