[Mristudio-users] Different Gradient Table of DTI from Philips Achieva 3T

[susumu mori]

Hi Hiquing,

It seems that the first table was created by a program not provided from
us??
The second table seems to be created from the software obtained from Kriby
Center in KKI?

Anyway, I can give some generic information.

1) In Philips, you can specify the order of 32+1 images. I believe the
default is b0 + 32 DWIs + calculated isotropically weighted image. You can
also choose to store 32 DWIs + b0 + calculated.

This is one reason of the difference

2) In DtiStudio, we use "100, 100, 100" to exclude images you don't need.
That is why the second table has 34 rows and the final raw is "100, 100,
100". Apparently, the second table was created specifically for DtiStudio.
The first table has only 33 rows because it ignored the last image.

This is the second reason of the difference.

3) Philips has two options of gradient tables; with and without gradient
overplus. If this option is "on", the table is designed to always use at
least 2 gradients. In this way, you can maximize the b-value efficiency and
shorten the echo time (thus higher SNR). Apparently the first table is
"off", because there is "1, 0, 0". The second is "on".

This is the third reason of the difference.

Hope this clarify the question. You need to know exactly what you did for
the above three points and grab the correct table.

Susumu

2010/9/14 黄海清 <basketballmouse at 163.com>

> Hi,
>
> I'm dealing with DTI data from Philips Achieva 3T. I tried two methods to
> compute the gradient table (32+1).
> (1) " dcm2nii.exe " with Philips dicom files
>          0         0         0
>     1.0000         0         0
>          0   -1.0000         0
>          0         0   -1.0000
>    -0.0424    0.1146    0.9925
>     0.1749    0.2005    0.9640
>     0.2323    0.1626    0.9590
>     0.3675   -0.0261    0.9296
>     0.1902   -0.3744    0.9076
>    -0.1168   -0.8334    0.5402
>    -0.2005   -0.2527    0.9465
>    -0.4958   -0.1345    0.8580
>    -0.0141    0.6281    0.7780
>    -0.7445    0.1477    0.6511
>    -0.7609   -0.3204    0.5643
>    -0.1809   -0.9247    0.3351
>    -0.6796    0.4224    0.5997
>     0.7771   -0.4707    0.4178
>     0.9242    0.1036    0.3677
>     0.4685    0.7674    0.4378
>     0.8817    0.1893    0.4322
>     0.6904   -0.7062    0.1569
>     0.2391   -0.7571    0.6080
>    -0.0578   -0.9837   -0.1703
>    -0.5368   -0.8361    0.1135
>    -0.9918    0.1207    0.0423
>    -0.9968   -0.0709    0.0379
>    -0.8724   -0.4781    0.1014
>    -0.2487   -0.9336   -0.2581
>     0.1183   -0.9919    0.0471
>     0.3376   -0.8415   -0.4218
>     0.5286   -0.8409   -0.1163
>     0.9969   -0.0550    0.0571
> (2) " DTI_gradient_table_creator_Philips_RelX.m " with Philips par/rec
> files
>    -0.6533   -0.2706   -0.7071
>    -0.2087   -0.6756   -0.7071
>     0.0197   -0.7068   -0.7071
>     0.4212   -0.5679   -0.7071
>     0.6899   -0.1549   -0.7071
>    -0.6535   -0.2707   -0.7069
>    -0.5000   -0.5000   -0.7071
>    -0.2929   -0.7071   -0.6436
>     0.2945   -0.7064   -0.6436
>     0.5150   -0.4861   -0.7061
>     0.7071   -0.2929   -0.6436
>    -0.7071   -0.4725   -0.5261
>    -0.4725   -0.7071   -0.5261
>     0.5555   -0.6439   -0.5261
>     0.7071   -0.4725   -0.5261
>    -0.7071   -0.7071   -0.0002
>     0.7071   -0.7071         0
>    -0.7071   -0.4725    0.5261
>     0.7071   -0.4725    0.5261
>     0.4725   -0.7071    0.5261
>     0.7071   -0.4725    0.5261
>    -0.6364   -0.4252    0.6436
>    -0.7060   -0.7060    0.0547
>    -0.2929   -0.7071    0.6436
>     0.2929   -0.7071    0.6436
>     0.7071   -0.7071    0.0078
>     0.7071   -0.2929    0.6436
>    -0.5847   -0.3977    0.7071
>    -0.7063   -0.7063    0.0489
>     0.0347   -0.7063    0.7071
>     0.7071   -0.7071    0.0115
>     0.7071         0    0.7071
>          0         0         0
>   100.0000  100.0000  100.0000
> They seem totally different. So can any person explain this problem? Thank
> you very much!
>
> Haiqing
>
>
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