[Mristudio-users] broken and thick fibers

[Durai Arasan]

Thanks!

On Sat, Mar 16, 2013 at 7:55 AM, susumu mori <susumu at mri.jhu.edu> wrote:

> 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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>>>>
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>>
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>
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