Hi Sangho,
Diffusion MRI tractography is typically asymmetric. So you will get a different tract if you go from the striatum to the DLPFC than if you go from the DLPFC to the striatum subdivisions. This means that the average FA value that you calculate across these tracts will also be different.
However, this asymmetry is caused by the tractography algorithm and has nothing to do with the direction of the underlying connectivity. So just because you are interested in the effect on striatum controlled by DLPFC, does not mean that tracking from the DLPFC will give you a more relevant tract than tracking from the striatum subdivisions. Both tracking from the DLPFC or from the striatum subdivisions will give you two different estimates of what the underlying WM tract might be (irrespective of which direction the WM tract runs in). If you decide to run both, you could either determine based on prior anatomical knowledge which of the two gives you more reliable results or just average them to get a single FA value for the tract.
Best wishes,
Michiel
> On 24 Jul 2019, at 09:20, Sangho Shin <[log in to unmask]> wrote:
>
> Hi,
>
> I have analyzed DTI data to know differences of tractography between striatum subdivision(associative striatum, limbic striatum, and seonsorimotor striatum) and DLPFC for patients with schizophrenia.
> When I started to analyze it, I put subdivisions of striatum in seed image and DLPFC in waypoint & termination mask. Then, I finally got FA value from tractography analysis. But I began to wonder if results from tractography of [striatum subdivisions ---> DLPFC] is different from that of [DLPFC ---> striatum subdivisions].
> Does FDT diffusion analysis have difference of FA value according to direction ( [striatum subdivisions ---> DLPFC] vs [DLPFC ---> striatum subdivisions])?
> If so, I think that I have to analyze it again from DLPFC in waypoint & termination mask to striatum subdivisions in seed image) because I should know an effect on striatum controlled by DLPFC.
>
> BW
>
> Sangho
>
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