Hi,
>GE and Siemens; for instance, the 2 manufacturers have a different
>direction for the EPI blips, which results in opposite direction EPI
>distortions
yes - per default. However, on Siemens you can freely change the PE and if
you rotate it by 180° you get the opposite.
Also the scanner drift is normally positive on Siemens and negative on GE
scanners.
Cheers,
Andreas
Am 20.06.12 01:30 schrieb "Walker, Lindsay (NIH/NICHD) [G]" unter
<[log in to unmask]>:
>There are quite a few papers that look at inter- and intra- site variance
>in DTI. For instance, take a look at:
>
>Walker L, Curry M, Nayak A, Lange N, Pierpaoli C; and the Brain
>Development Cooperative Group. A Framework for the Analysis of Phantom
>Data in Multicenter Diffusion Tensor Imaging Studies, Hum Brain Mapp.
>2012 [Epub ahead of print]
>
>Gouttard S, Styner M, Prastawa M, Piven J, Gerig G. (2008): Assessment of
>reliability of multi-site neuroimaging via traveling phantom study. Med
>Image Comput Comput Assist Interv 11(Pt 2):263-70.
>
>Pagani E, Hirsch JG, Pouwels PJ, Horsfield MA, Perego E, Gass A,
>Roosendaal SD, Barkhof F, Agosta F, Rovaris M and others. (2010):
>Intercenter differences in diffusion tensor MRI acquisition. J Magn Reson
>Imaging 31(6):1458-68.
>
>Vollmar C, O'Muircheartaigh J, Barker GJ, Symms MR, Thompson P, Kumari V,
>Duncan JS, Richardson MP, Koepp MJ. (2010): Identical, but not the same:
>intra-site and inter-site reproducibility of fractional anisotropy
>measures on two 3.0T scanners. Neuroimage 51(4):1384-94.
>
>Zhu T, Hu R, Qiu X, Taylor M, Tso Y, Yiannoutsos C, Navia B, Mori S,
>Ekholm S, Schifitto G and others. (2011): Quantification of accuracy and
>precision of multi-center DTI measurements: a diffusion phantom and human
>brain study. Neuroimage 56(3):1398-411.
>
>While not all of these address specifically scanner manufacturer
>differences, they highlight important issues to consider when combining
>data from multiple imaging centers, even if the protocol is maintained
>exactly the same at all centers.
>
>In our experiences there are distinct differences between data acquired
>on GE and Siemens; for instance, the 2 manufacturers have a different
>direction for the EPI blips, which results in opposite direction EPI
>distortions (expansion/contraction).
>
>Hope this helps.
>
>Lindsay.
>
>
>
>________________________________________
>From: Michael Harms [[log in to unmask]]
>Sent: June 19, 2012 11:05 AM
>To: [log in to unmask]
>Subject: Re: [FSL] differnet MRI scanner
>
>Depending on how the protocols were set up, there could be a lot of
>differences -- b-values, direction and number of b-vectors, TR, TE,
>voxel sizes, etc, etc. Were all those matched across scanners?
>
>cheers,
>-MH
>
>On Tue, 2012-06-19 at 22:28 +0800, Peng Syu-Jyun wrote:
>> Dear exports
>>
>> I have three sets DTI data that scan in different MRI scanners of all
>> control subjects, include 1.5 T GE, 1.5 T Siemens and 1.5 T Philips
>> scanner.
>>
>> I have 20 normal subjects, so total 60 sets DTI data.
>>
>> Each subjects have three sets DTI obtained in three different MRI
>> scanners.
>>
>> What differences between the three sets DTI data of subjects?
>>
>> Could the MRI regarded as the smae in differnet MRI scanner (magnetic
>> field are all 1.5 T)?
>>
>> Have any related paper?
>>
>> Best regards,
>>
>> Syu-Jyun
>>
>>
>>
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