CATNAP : Technical Notes

(Coregistration, Adjustment, and Tensor-solving, a Nicely Automated Program)

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BUG: Eigenvalue Scaling (April 18, 2007)


PAR File Format (April 11, 2007)



“Sort Images” Export Option (April 11, 2007)


1)  If you are using a user defined gradient table without the “OVERRIDE” option, then do NOT specify the 0,0,0 (b0’s) in the diffusion weighting directions text file. The location of the b0’s within the file will be automatically determined based on the PAR version and “sort images” option.


2) If you are using the “OVERRIDE” option, then you must specify the order to b0’s and diffusion weighted images in the diffusion weighting directions text file. Indicate b0’s with a direction of 0,0,0.


3)  CATNAP is using the following logic to place the b0’s:


Version   sort_images     order            b=0 position in REC file

 V3          yes               volume            first volume

 V3          no               NOT SUPPORTED

 V4          yes               volume            first volume

 V4          no                slice                 first sub volume for slices

 V4.1        yes               volume           last or second last volume

 V4.1        no                slice                first sub volume for  slices


4) IMPACT on gradient tables for DTIStudio:


% This code writes out gradient tables for DTIStudio.  The gradient table % provided will reflect the position of the b=0 volume in the REC file (it % will be first, last or second last depending on the table above).  For % the case of V4.1 sort_images = y, the b=0 volume is last.  For the case % of V4.1 sort_images = 'n', the b=0 volume must be listed first to work % with DTIStudio and image sequence "slice by slice" must be selected



Last Updated: Tuesday May 27, 2008

© Copyright 2006, Bennett Landman. All rights reserved.