[Mristudio-users] Is better to do 3 DTI series or just one well done?

[susumu mori]

I wouldn't push the resolution that much. I even hesitate to use 128x128,
unless we can use SENSE factor of 4 so that the echotrain is 128/4 =32

On Thu, Dec 10, 2009 at 1:33 PM, Lucas Lessa <lucas_lessa at yahoo.com.br>wrote:

> Dr. Susumu Mori you helped me a lot.
> I'm using 3 repetions of a 33 dir DTI in a Philips 1.5T (the voxel is about
> 2.2mm.) when I want to do an exam for a research, for the real life I use
> just one repetion.
> Indeed the SNR is much better with 3 repetions, but just in DTI Studio,
> because Philip's software don't handle the 3 series like one.
> What do you think in increase my resolution to 256x256 in this scanner?
> Will the exam take so long? Can I use just 2 repetitions?
> Thank you.
>
> Lucas Lessa.
>
>
>
> --- Em *qui, 10/12/09, susumu mori <susumu at mri.jhu.edu>* escreveu:
>
>
> De: susumu mori <susumu at mri.jhu.edu>
> Assunto: Re: [Mristudio-users] Is better to do 3 DTI series or just one
> well done?
> Para: "DTI Studio, ROI Editor, Landmarker Questions/Support" <
> mristudio-users at mristudio.org>
> Data: Quinta-feira, 10 de Dezembro de 2009, 15:22
>
>
> If you are using a 1.5 T scanner, I think 2.5 mm isotropic resolution is a
> good compromise between scanning time and SNR. With a 30-orientation scheme,
> you may want to do at least two repetition (total 60 DWIs) to get a decent
> SNR. If you want to increase the resolution, you need more dwis and a longer
> scanning time.
>
> What is important is the total number of images, in this case 60. So, if
> you are using a 15-orientation scheme, you need 4 repetitions. A
> 30-orientation scheme should take about 4-5min in Siemens and Philips. GE
> may take 7-8 min in some versions because of gradient overheating precaution
> (TR can't be too short). So, two repetitions (total 60 dwis) should take
> 8-10 min in Siemens/Philips. This is certainly a long scan, especially for
> clinical. If time is important, you can do one repetition (total 30 dwis),
> scarifying the SNR. In this case, you definitely don't want to increase the
> resolution, which would make the SNR worse.
>
> For 3T, 30 dwis can give you a decent SNR with 2.5mm resolution. Or if you
> stick with a 60 dwis protocol, you can use 2.2 mm resolution. I have seen
> nice 2.0 mm resolution with the latest head coils. For 2.2 mm, you need to
> use 112x112 matrix. Please note that larger matrix leads to more distortion.
> Because 3T has larger distortion than 1.5 T, using a larger matrix in 3T is
> not a good idea in general.
>
> Hope it helps.
>
> Susumu
>
> On Thu, Dec 10, 2009 at 9:47 AM, Lucas Lessa <lucas_lessa at yahoo.com.br<http://br.mc1102.mail.yahoo.com/mc/compose?to=lucas_lessa@yahoo.com.br>
> > wrote:
>
>>   Good morning,
>>
>> As I said in aonther post, I'm in the middle of a DTI study that,
>> obsviously, uses DTI studio to process the data.
>> The other researcher brought (a think from John Hopkins) a model that uses
>> 3 DTI series, just to increase the ratio between sign/noise.
>> The exams are taking so long and I would like to increase the resolution
>> from 112x110 to 256x256, and maybe, 512x512.
>> Is this a good idea? Or it's better to continue making the exams with the
>> 3 DTI series?
>> And wich is the bennefit of doing 3 DTI series (the vendor software only
>> uses one at a time)?
>> One more time thank you.
>>
>> Lucas Lessa
>> São Paulo/Brazil
>>
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