[Mristudio-users] DTI analysis question

[susumu mori]

The order is correct except for the step #3, which is not necessary.
I wonder how you did to average the scan because DtiStudio doesn't offer a
function to average scans, I thought.

For the tensor fitting with multiple-repetition data, you don't need average
the data before the tensor calculation. This is very similar to a simple XY
plot linear fitting. Suppose you have 8 measurement points to perform Y=aX+b
fitting. If the 8 points are spread along the X axis (say, at X = 1, 3, 5,
7, 9, 11, 13,15), you just perform the fitting. What if the 8 points are at
X = 1, 5, 9, 13? This means, at each X value, there are two measurement
points. Do you calculate an average value for each X value before the
fitting? I think in most case you do the same 8-point fitting in this case
too.

Likewise, if you have, for example 3 sets of 30-orientation measurements,
you don't have to reduce the data to a single 30-orientation before tensor
calculation. You can just submit 90-point linear fitting.

Hope this is clear.

Also for the step #2, Yes, AIR is for co-registration and if you choose
Affine, it also does Eddy current correction.

On Tue, Jan 19, 2010 at 2:36 AM, Ryan <wmcgarry at gmu.edu> wrote:

> Hello everyone,
>    I want to confirm that I have the correct order for DTI analysis
> performed with a Siemens scanner using the Mosaic option, where several sets
> are collected. After going through the mailing list, I'm still not certain
> if this order is correct:
>  1) Load the multiple sets of images
>  2) Perform auto registration (is this the same as co-registration? if not,
> how do I do co-registration?)
>  3) Average the AIRed scans
>  4) Perform tensor calculations
>
>
> Thank you very much!
>
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