[Mristudio-users] broken and thick fibers

[susumu mori]

Resolution has impacts on many things.
Of course, the higher the resolution, the smaller tracts you can
delineation more accurately, but you would expect more noise.
because scanning time is usually limited, higher resolution leads to lower
SNR.
So the impact on tractography is very complicated.
As for the noise, I attached a paper from our lab.

On Fri, Mar 8, 2013 at 6:59 PM, Durai Arasan <durai23 at gmail.com> wrote:

>
>
> On Fri, Mar 8, 2013 at 6:58 PM, Durai Arasan <durai23 at gmail.com> wrote:
>
>> Thanks! The gradient table was extracted from the dicom header.
>>
>> As you can see in the picture in the next message, no flipping gives rise
>> to best (corpus callosum) results among all 7 permutations. This is a new
>> siemens scanner.
>>
>> Can anyone comment on the effect of pixel size, slice thickness and noise
>> on fiber quality?
>>
>> On Fri, Mar 8, 2013 at 7:20 AM, susumu mori <susumu at mri.jhu.edu> wrote:
>>
>>> As Anonim mentioned, the most common mistake is the sign of the gradient
>>> table.
>>> Please read page 23 of the manual here (
>>> https://www.mristudio.org/wiki/user_manual).
>>> If you feed a gradient table based on a generic table, you need to
>>> figure out the +/- sign of the vector elements.
>>>
>>> Recent DICOM headers contain vector information with correct +/- signs.
>>> So, it is easier to use the function to extract the gradient table from the
>>> header.
>>>
>>>
>>> On Thu, Mar 7, 2013 at 1:35 PM, Anonim <albnet at gmail.com> wrote:
>>>
>>>> Try flipping the eigenvector for direction X, Y, or Z. Its typical to
>>>> have short fibers when one of the eigenvectors need to be flipped.
>>>>
>>>> Dorian
>>>>
>>>> 2013/3/7 Durai Arasan <durai23 at gmail.com>
>>>>
>>>>> Hi all
>>>>>
>>>>> I am tracking with data that has slice thickness = 3 and pixel size =
>>>>> 1.65.
>>>>>
>>>>> I have a lot of broken fibers i.e. the path of the fiber is
>>>>> interuppted.
>>>>>
>>>>> My fibers are also quite thick (large diameter) and less dense (low
>>>>> number of fibers/area).
>>>>>
>>>>> Any comments on why this is observed?
>>>>>
>>>>> Thanks
>>>>>
>>>>>
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>
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