[Mristudio-users] Re: re： How to do a Tailarach transformation?

[Seongjin]

Dear Susumu,

Do you have relevant literature on your opinion:

"...In reality, within practical imaging time, I don¡¯t think you can observe
such effect clearly. Our past measurement (Landman et al, NeuroImage)
suggests once you have 12-orientation or more, you don¡¯t see much
differences..."

If you had, could you share the literature?

Thanks.

- SC


2009/4/7 susumu <susumu at mri.jhu.edu>

>  Hi Jinsong,
>
>
>
> It depends on whom you ask the question, but here is my opinion.
>
>
>
> When you are using diffusion ¡°tensor¡± imaging, all data will be fitted to
> obtain only the 6 tensor elements. Therefore, you need only 6 directions
> mathematically. However, such measurement takes only less than 1 min and do
> not have enough SNR (signal-to-noise ratio). To enhance the SNR, you need to
> acquire more data.
>
>
>
> Usually people spend 4-10 min of time for DTI, in which you can acquire
> about 30 ¨C 100 images. Then you have several options. For example, you can
> repeat the 6-orientation measurement 5 times (total 30) or one
> 30-orientation measurement within the same amount of time (should be within
> 5 min).
>
>
>
> Purely from mathematical point of views, I don¡¯t think 6-direction x 5 vs
> 30-orientation have that much difference in terms of overall SNR. However,
> it is true that the 6-orientation measurement has more orientation-dependent
> inhomogeneity in SNR. This means, certain orientations can be measured with
> higher SNR while some orientation has poorer SNR. By adopting more
> orientations, such orientation-dependent SNR profile becomes more
> homogeneous (less orientation dependent).
>
>
>
> In reality, within practical imaging time, I don¡¯t think you can observe
> such effect clearly. Our past measurement (Landman et al, NeuroImage)
> suggests once you have 12-orientation or more, you don¡¯t see much
> differences.
>
>
>
> Some researchers are seeking for diffusion ¡°more than one tensor¡± imaging.
> If you want it, you may need more than 30 orientations and higher b-values.
> So, you may need to design very different protocols.
>
>
>
> Susumu
>
>
>
>
>
>
>  ------------------------------
>
> *From:* mristudio-users-bounces at mristudio.org [mailto:
> mristudio-users-bounces at mristudio.org] *On Behalf Of *jinsong tang
> *Sent:* Tuesday, April 07, 2009 12:52 PM
> *To:* DTI Studio, ROI Editor, Landmarker Questions/Support
> *Subject:* [Mristudio-users] re£º How to do a Tailarach transformation?
>
>
>
> Hello everyone,
>
>
>
> Now the Siemens  3.0 T MRI scanner can collect 30  non-collinear
> directions diffusion data. Does this helpful for fiber tracking ?
>
>
>
> But I found most paper only use 12 directions. Does anybody know why?
>
>
>
> Best,
>
>
>
> Jinsong
>
>
>  ------------------------------
>
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