[Mristudio-users] high Rd value

[susumu mori]

2011/3/6 hanaie <dc02hana at m6.gyao.ne.jp>:
> Dear DTI experts,
>
>
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> After fiber tracking, I obtained FA, trace , Rd, Ad value.
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> Eigen Value - 0
>
>         Max. of ImgVal:   4.647e-003  Min. of ImgVal:   0.000e+000
>
>         Mean of ImgVal:   2.179e-003  Std. of ImgVal:   5.147e-004
>
> Radial Diffusivity
>
>         Max. of ImgVal:   1.998e-003   Min. of ImgVal:   0.000e+000
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>         Mean of ImgVal:   6.584e-004　 Std. of ImgVal:   3.607e-004
>
> Tensor - Trace
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>         Max. of ImgVal:   8.643e-003   Min. of ImgVal:   0.000e+000
>
>         Mean of ImgVal:   3.496e-003  Std. of ImgVal:   1.130e-003
>
> Anisotropy - FA
>
>         Max. of ImgVal:   0.8998    Min. of ImgVal:   0.000e+000
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>         Mean of ImgVal:   0.6589   Std. of ImgVal:   0.1486
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>
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> And , I have questions.
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> Q1. When I report these values, which number must I report? Mean of Imgval?

that's correct.

>
> Q2. When I report MD value, Can I divide trace value by 3?

that's correct.

>
> Q3. I guess that these values obtained are too high, especially Ad and Rd.

I believe that MD should be about 0.9-1.0. So your reported value is a
bit high.
Please make sure that you used correct b-values. For example, if you
used b=1,000 for data acquisition and used b=800 for processing, MD
becomes higher.
Also, smaller b-value tends to give higher MD. Many labs use b=1,000.
If you are using b=700, then your MD becomes a bit higher even if you
used the correct b-value for processing. This is because diffusion
signal decay is not mono-exponential and decays faster in low b-value
range than high b-value range.
>
>    Why happen like this? Values are for superior cerebellar peduncle.
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>
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> Please give me any suggestion.
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> Many thanks.
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>
>
> Ryuzo
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