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

[susumu]

Here it is.

  _____  

From: mristudio-users-bounces at mristudio.org
[mailto:mristudio-users-bounces at mristudio.org] On Behalf Of [Seongjin]
Sent: Tuesday, April 07, 2009 10:31 PM
To: DTI Studio, ROI Editor, Landmarker Questions/Support
Subject: [Mristudio-users] Re: re£º How to do a Tailarach transformation?


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

 

 

 


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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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