[Mristudio-users] Slice thickness of DTI

[Santosh Yadav]

 Thanks a lot Sir,


I have another question regarding DTI data; I have longitudinal DTI data of
3 time points. First time point have 4 averages second time point have 2
averages and third time point have 4 averages, can I combine these data
sets?

So finally the question is what the effect of averaging of DTI data, is it
going to the change the DTI matrix such as FA and Trace?


With best Regards,


On Mon, Nov 26, 2012 at 2:31 AM, susumu mori <susumu at mri.jhu.edu> wrote:

> Hi Santosh,
>
> Practically, the slice thickness, which is the thinner the better, is
> determined by SNR.
> If you use 2.5 mm, you need about 50-55 slices to cover the entire brain.
> 2.2 mm needs 55-60 and 2mm needs more than 60. These are all without gaps.
>
> With 5-6 min scans, you can acquire about 40-50 DWIs for 2.5mm/50-slice 3D
> data. These numbers decrease as the thickness become thinner and thus more
> slices are required and takes longer time.
>
> 40-50DWI means about 4 repetitions of 12-orientations.
>
> If you use a 1.5T, you may need more than 60 DWIs with 2.5mm, which takes
> about 7-8min. With thinner slices (e.g. 2.2mm), you need longer scans to
> achieve good SNR.
>
> With a 3T, 30-40 DWIs would give decent SNR with 2.5mm. With 2-2.2mm
> slice, you want more than 50-60 DWIs (5-8min).
>
> These numbers are to achieve a good SNR, which depends on my subjective
> judgement. So different people could recommend different numbers, but they
> may not be that much different.
>
> As for image distortion, the most important factor is the size of the
> image matrix; the smaller the better (I assume that you already use
> parallel imaging, which reduces the matrix size into half).
>
> For example, 128x128points / 256x256mm and 96x96/192x192mm both give the
> same 2mm resolution, but 96x96 would give better (less) distortion and
> better SNR.
>
> On Mon, Nov 26, 2012 at 1:28 AM, Santosh Yadav <
> santoshyadav20076 at gmail.com> wrote:
>
>> Hi DTI experts,
>>
>> Thanks for great supports!
>>
>> I would like know the recommended slice thickness and gap between the
>> slice for DTI data acquisition for 12 directions. Is higher
>> Slice thickness( more that 3 mm) have partial volume effect?
>>
>> Second question: Is eye open during the DTI acquisition have any impact
>> on DTI distortion or image quality?
>>
>> With Best Regards,
>>
>> Santosh
>>
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-- 
With Best Regards,

Neuroscience and MR Research Program

Department of Medicine, Queen's Medical Center

University of Hawaii

1356 Lusitana Street, 7th Floor, Honolulu, HI 96813

Phone No. 808-220-7152

Fax No.  808-545-8970
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