[Mristudio-users] transverse diffusion parameters

[susumu mori]

For "Mean diffusivity", please use Trace. Trace/3 = MD.

Color map 0, 1, 2 show orientation information of eigen vector 0, 1, 2.
Usually we use only color0.



On Thu, Mar 7, 2013 at 12:27 AM, Shaimaa Abdelsattar
<shaimaa96 at hotmail.com>wrote:

> Hi,
> After ADC calculations, I found ADC map corresponding to each gradient,
> how can I find one averaged ADC to measure ADC in a specific ROI ?
> Another question, please, what is meant by color map o, 1, and 2
>
> Thank you for your efforts
>
>
> On Mar 7, 2013, at 3:47 AM, "susumu mori" <susumu at mri.jhu.edu> wrote:
>
> I think it doesn't make too much sense to go below 0.15 for FA threshold.
> As FA goes down, the fiber orientation has less meaning; there is no
> orientation for a sphere and because of noise, even perfectly sphere media
> could be FA = 0.1.
>
> I think Cut is a better approach. Trajectory in between two ROIs has a
> strong anatomical constraint and has very small false positive.
>
> If you are interested in transverse diffusivity, you can use
> (Evalue1+Evalue2)/2. (assuming 3 Evalues are numbered 0, 1, 2).
>
> 2DFA2-3 and FA1-3 are metrics to measure difference between Evalue1 and 2
> and Evalue0 and 2. We calculate them, but honestly, I'm not sure if it has
> much meaning.
>
>
>
> On Wed, Mar 6, 2013 at 12:46 PM, Prachi Dubey <pxd2010 at gmail.com> wrote:
>
>>
>> Thank you Hangyi thats very helpful.
>>
>> Do you propose it is best to stick to 0.2 threshold? or there is another
>> lower but reliable threshold. My priorty is to get the most reproducible
>> results for mean tract diffusion parameters.
>>
>> also what do you think will be more reliable for quantitative purposes,
>> using cut function to exclude the fiber edge or using the entire tract.
>>
>> Also would like to hear your comments on eigen value1 and 2 and 2DFA2-3
>> and 2DFA1-3. And how these are computed, how specifically they differ from
>> FA and Trace.
>>
>> Prachi
>> On Wed, Mar 6, 2013 at 12:36 PM, Hangyi Jiang <hjiang at jhmi.edu> wrote:
>>
>>>
>>> personally,  I think 0.1 is too low to get reliable (or consistent)
>>> fiber tracking results.
>>>
>>> best,
>>>
>>> hangyi
>>>
>>>
>>>  ------------------------------
>>> *From:* mristudio-users-bounces at mristudio.org [
>>> mristudio-users-bounces at mristudio.org] on behalf of Prachi Dubey [
>>> pxd2010 at gmail.com]
>>> *Sent:* Wednesday, March 06, 2013 12:10 PM
>>> *To:* DTI Studio, ROI Editor, DiffeoMap Questions/Support
>>> *Subject:* [Mristudio-users] transverse diffusion parameters
>>>
>>>   Hi,
>>>
>>> Any thoughts on how low one could go on FA threshold for tracking
>>> without introducing too much noise. I am using FA=0.2, and a lot of my
>>> patients have very severely atropic tracts and it is excluding a lot of the
>>> data. I can track more fibers if go as low as 0.1 but that makes me worry
>>> if I am introducing tracking error.
>>>
>>> Also what has your experience been with transverse diffusion values,
>>> eigen value1 and 2 and 2DFA2-3 and 2DFA1-3. In my dataset they are more
>>> sensitive than FA or Trace.
>>>
>>> Any thoughts, comments appreciated. Prachi
>>>
>>> --
>>>
>>> Prachi Dubey, MD MPH
>>> ph:4109614841
>>>
>>> _______________________________________________
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>>>
>>
>>
>> --
>>
>> Prachi Dubey, MD MPH
>> ph:4109614841
>>
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