I am on my way for an ovserseas 1 month trip. I hope the info below is useful:
1. I would also analyze water phantom collected form these centers over the span of data acquistion, this is helpful to isolate gradient biases, b-factor calibration. Phantom temperture may alter estimated diffusivities, clearly not seen on humans, but anisotropy will provide a quality control measure as described in Hasan MRI 2007 (see list below). If your encoding scheme is multifacted icosahedral then this data have a huge amount of potential as far as DTI-SNR bias analysis (Hasan and Narayana 2003)
2. Search Pubmed for publication on the topic "multi-center, intercenter, multicenter and DTI". In particular the work of Pagani et al.. JMRI 2010 (see below) which may answer in part your question, variations do occur as implementation of SE-EPI may provide different diffusion parameters, distortions,....I am still assuming you have identical TE, TR, encoding, b-factor, voxel dimensions.
3. If the goal is to spatially normalize the three data sets or analyze it using alterntaive methods (see Hasan et al 2011). SPM preprocessing may be tolerant to small variations between scanners. But, this is group analysis assuming the subjects are close in age/gender. If the ages are say 18-40 years, you may also test the results from each scanner as function of age as some trends are now well established and the number you have warrant detecting age linear trends on young adults. Then compare the age trends predicted (slopes) on each scanner. This is different from just comparing group means which may/will differ if paired t-test is used, if the age-vs. DTI trends between all scanners are analogous and are statistically comparable then one may come up with some novel ways of adjusting the values "global -ancova". Since DTI scalar metrics are scale-independent, there is no theretical basis for such scaling unless it is SNR or some systematic-bias related (Hasan and Naraya MRM 2003).
Suggested References
1. Search pubmed multi-center, intercenter, multicenter and DTI
2. Pagani E, Hirsch JG, Pouwels PJ, Horsfield MA, Perego E, Gass A, Roosendaal SD, Barkhof F, Agosta F, Rovaris M, Caputo D, Giorgio A, Palace J, Marino S, De Stefano N, Ropele S, Fazekas F, Filippi M. Intercenter differences in diffusion tensor MRI acquisition. J Magn Reson Imaging. 2010 Jun;31(6):1458-68.
3. Hasan KM. A framework for quality control and parameter optimization in diffusion tensor imaging: theoretical analysis and validation Magn Reson Imaging. 2007;25(8):1196-202.
4. Hasan KM, Narayana PA. Computation of the fractional anisotropy and mean diffusivity maps without tensor decoding and diagonalization: Theoretical analysis and validation. Magn Reson Med. 2003;50(3):589-98.
5. Hasan KM, Walimuni IS, Abid H, Hahn KR. A review of diffusion tensor magnetic resonance imaging computational methods and software tools.
Comput Biol Med. 2011;41(12):1062-72.
Khader M Hasan, PhD
Associate Professor of Radiology
MSE 168, Tel 713 500 7690 (FAX 713 500 7684)
University of Texas Health Science Center at Houston
Medical School
Diagnostic and Interventional Imaging
Magnetic Resonance Imaging Research Division
Diffusion Tensor Imaging Lab, Tel 713 500 7683
http://www.uth.tmc.edu/radiology/faculty/khader-m-hasan/index.html<http://www.uth.tmc.edu/radiology/faculty/hasan.html>
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From: SPM (Statistical Parametric Mapping) [[log in to unmask]] On Behalf Of Peng Syu-Jyun [[log in to unmask]]
Sent: Tuesday, June 19, 2012 9:28 AM
To: [log in to unmask]
Subject: [SPM] differnet MRI scanner
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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