[Mristudio-users] How to recalculate gradient table of Philips DICOM files with 'gradient overplus' on

[Susumu Mori]

Hi Ming,

Gradient Overplus table needs to be recalculated IF your image has oblique
angles. If your images were acquired with the simple axial plane, there is
no need for recalculation.
Very often the axial plane is tilted depending on the orientation of the
head position. Then you need to regenerate a new table by feeding oblique
angle information to one of these programs.

This is also true for certain Siemens data.

If you are using DtiStudio and DICOM files, DtiStuio support automatic
reading of DICOM b-table and axial oblique information and recalculation of
the table by choosing "rotate gradients if applicable" option, but this
works only for certain DICOM versions. So you need to test this function.

If your DICOM files are not supported, you need to rely on one of the
programs you listed. For the #1 program, I believe the calculator only
needs the b-table and oblique angle information, although the angle
information is obtained from the PAR file. I'm not sure where is the
corresponding information in DICOM header.

Susumu

On Wed, Jul 13, 2016 at 11:51 AM, Ming Peng <datou06415 at gmail.com> wrote:

> Hi:
>   I have a dataset of DICOM files (a directory contains lots of .dcm
> files), and these data are collected from Philips device with "gradient
> overplus" option on.
>   After googling, I found that the gradient table of these data should be
> recalculated if the "gradient overplus" option is on for Philips devices.
> And I found several tools:
>   1 - DTI_gradient_table_creator
>
> http://godzilla.kennedykrieger.org/~jfarrell/software_web.htm#DTI_gradient_table_creator
>
>
>      This tool can only parse data in PAR/REC format, however my data are
> thousands of separate .dcm files from a single patient.
>
>   2 - DTI gradient table
>
> http://jp.mathworks.com/matlabcentral/fileexchange/41876-dti-gradient-table/content/dti_grad_table.m
>
>
>      It only works for a multi-frame dcm file.
>
>    My questions is:
>       a - How can i recalculate the gradient table from these .dcm files ?
>       b - Is there any other tools suited for this situation ?
>
>    Thanks
>
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