mriconvert: Difference DWI Gradient Values

Wed Apr 17 06:23:19 PDT 2013

Dear MRIConverter Group,

I am converting DICOM data from a Siemens Espree 1.5T machine for Fiber
Tracking. Looking at the converted files I see that there is a difference
between the raw gradients and the gradients once converted. I am interested
to know where these differences come from. What pre processing steps are
performed on the data during conversion? Is it a correction? Is it
recomended to do that instead of use the raw vector gradients?

I have included the gradient values I have obtained from the software here
as reference. I have also summarized my findings below.

Your help in helping me to identify the source of these differences is much
appreciated!!

Best Regards

Fernando
*1. Raw Info of gradient*

File: RawDicomGradient.txt (The gradients are not sort as the output of
other tools)
0.000000 0.000000 0.000000
0.999977 0.006051 0.003027
-0.000006 -0.999982 0.006006
-0.024989 -0.653018 -0.756930
0.588672 0.769595 -0.247364*
...

2.MRIConverter (dcm2nii)*
File:MRIConverter.txt
dw_scheme:0.000000 0.000000 0.000000
dw_scheme:0.999660 -0.004982 -0.025588
dw_scheme:-0.008132 0.962882 -0.269799
dw_scheme:-0.052352 0.419028 -0.906463
dw_scheme:0.587622 -0.807974 -0.043334
...
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dw_scheme:0.000000 0.000000 0.000000 
dw_scheme:0.999660 -0.004982 -0.025588 
dw_scheme:-0.008132 0.962882 -0.269799 
dw_scheme:-0.052352 0.419028 -0.906463 
dw_scheme:0.587622 -0.807974 -0.043334 
dw_scheme:-0.254737 -0.733768 -0.629836 
dw_scheme:-0.900807 -0.354889 -0.250200 
dw_scheme:0.779287 -0.043566 -0.625152 
dw_scheme:0.216927 0.819093 -0.531064 
dw_scheme:0.926104 0.050032 -0.373937 
dw_scheme:0.516203 -0.767101 0.380909 
dw_scheme:0.364528 -0.707876 0.605005 
dw_scheme:0.480800 -0.438597 0.759252 
dw_scheme:-0.505648 -0.594450 -0.625259 
dw_scheme:-0.634859 0.539285 -0.553286 
dw_scheme:-0.553573 0.126291 0.823169 
dw_scheme:-0.825994 -0.562842 -0.030703 
dw_scheme:0.907918 0.089521 0.409476 
dw_scheme:0.317241 -0.307796 0.897006 
dw_scheme:0.130281 -0.860703 0.492155 
dw_scheme:-0.789503 0.514475 0.334665 
dw_scheme:0.500618 0.763005 -0.408907 
dw_scheme:-0.772575 0.316136 0.550623 
dw_scheme:0.944140 -0.286775 -0.162359 
dw_scheme:0.209225 0.598265 -0.773501 
dw_scheme:0.008168 0.094358 0.995505 
dw_scheme:0.217295 -0.974208 0.060838 
dw_scheme:0.770890 -0.636057 -0.034046 
dw_scheme:-0.189651 0.092205 -0.977512 
dw_scheme:-0.133288 0.889217 0.437638 
dw_scheme:0.878364 0.352739 -0.322570 
dw_scheme:-0.540875 0.446838 0.712594 
dw_scheme:-0.409028 -0.119019 -0.904727 
dw_scheme:-0.276957 0.069938 0.958334 
dw_scheme:-0.357731 -0.387825 -0.849482 
dw_scheme:-0.960757 -0.271761 0.055602 
dw_scheme:-0.966704 0.148988 -0.208054 
dw_scheme:0.456273 -0.875116 0.161203 
dw_scheme:-0.779281 0.583366 -0.228920 
dw_scheme:0.689759 0.238781 -0.683532 
dw_scheme:-0.715031 -0.180438 -0.675406 
dw_scheme:0.690700 0.651160 0.314522 
dw_scheme:-0.154711 -0.885548 -0.438029 
dw_scheme:-0.759949 0.226678 -0.609176 
dw_scheme:-0.125209 0.640537 -0.757651 
dw_scheme:0.571798 -0.728414 -0.377438 
dw_scheme:-0.111687 -0.585437 -0.802988 
dw_scheme:-0.550831 -0.834573 -0.008565 
dw_scheme:0.850048 -0.363342 0.381314 
dw_scheme:0.345057 -0.748552 -0.566221 
dw_scheme:-0.160292 0.629922 0.759937 
dw_scheme:-0.713324 -0.672033 0.198847 
dw_scheme:0.443302 0.821127 0.359490 
dw_scheme:0.480749 0.524888 -0.702406 
dw_scheme:-0.141452 -0.261268 0.954846 
dw_scheme:0.437371 0.196590 -0.877530 
dw_scheme:0.377582 -0.901979 -0.209443 
dw_scheme:-0.730093 -0.422954 -0.536726 
dw_scheme:0.262754 0.958008 0.114811 
dw_scheme:0.028305 0.353836 0.934879 
dw_scheme:0.031438 -0.986605 -0.160068 
dw_scheme:0.595838 -0.085028 0.798591 
dw_scheme:-0.255390 0.406141 0.877397 
dw_scheme:0.706009 0.497844 -0.503690 
dw_scheme:0.260205 0.947629 -0.185183 
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0.000000 0.000000 0.000000 
0.999977 0.006051 0.003027 
0.588672 0.769595 -0.247364 
-0.235606 0.529620 -0.814858 
0.232833 -0.931893 -0.278145 
0.936957 -0.143446 -0.318645 
0.457672 0.634826 0.622521 
-0.486541 0.394878 -0.779326 
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0.895146 0.034351 0.444449 
0.290032 0.545698 0.786191 
0.512713 -0.841960 -0.168012 
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0.215378 0.955018 -0.203843 
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0.838155 0.461412 0.290851 
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0.265658 -0.959774 0.090885 
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0.504485 0.846627 0.169462 
-0.578139 0.100860 0.809681 
0.115389 0.964051 0.239355 
0.948608 0.238764 -0.207690 
0.771572 0.608426 -0.185726 
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0.451215 0.889412 -0.073157 
0.680890 -0.533496 0.501768 
0.582930 0.600907 -0.546903 
0.361988 0.566348 -0.740415 
0.501703 -0.694114 -0.516237 
-0.713557 0.252565 -0.653488 
0.571461 0.306769 0.761134 
-0.024989 -0.653018 -0.756930 
0.797778 -0.123929 -0.590078 
0.346117 0.850191 0.396710 
-0.824690 0.525698 -0.208635 
-0.799240 -0.408861 0.440509 
0.232449 -0.786492 -0.572186 
-0.160072 -0.359594 -0.919277 
-0.381534 -0.138332 -0.913945 
-0.772024 -0.630319 -0.081712 
-0.141411 0.729213 -0.669516 
-0.087400 0.340505 -0.936172 
-0.183150 -0.397391 0.899186 
-0.170181 0.513098 0.841290 
0.259156 -0.887052 0.382069 
-0.281740 -0.150709 0.947581 