Hi Frederique,
> This means that my preT data were acquired on Scanner#1 and my postT data
> on Scanner#2. The TRs and TEs are different.
I think you're in trouble here because intrinsically, you will not be
able to statistically tease apart the effect of scanner vs. that of
treatment. Do you have controls on scanner 1 vs. scanner 2? Then you
could do patients scanner1) vs controls(scanner1) and patients(scanner2)
vs. controls(scanner2). The differences could be hypothesized to be the
result of treatment, but I fear you will not find much in such a design.
> For instance, would it be acceptable/legal to bring my Patients vs
> Controls contrasts (con1_preT and con2_postT) to a second level analysis
> to explore the interaction I am intested in?
I would think that perhaps this lessens the effect of different
sequences but I don't know if it is legal or not :)
> Is there another way I can process my data that would enable me control
> for the effect of scanner change?
You could use "scanner" as a covariate, but only if you do not have a
perfect correlation between treatment and scanner (which currently you
do). In other words, if you scan more patients, then you will have some
scanned on the old and some scanned on the new, and then you could use
scanner as a covariate of no interest somewhere down the line. It will
still be a not-very-clean-design, though...
> Any help would be greatly appreciated as these treatment studies are very
> time-consuming and I really hope I can still use my data.
I bet. Good luck!
Marko
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Marko Wilke (Dr.med./M.D.)
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Universitäts-Kinderklinik University Children's Hospital
Abt. III (Neuropädiatrie) Dept. III (Pediatric neurology)
Hoppe-Seyler-Str. 1, D - 72076 Tübingen
Tel.: (+49) 07071 29-83416 Fax: (+49) 07071 29-5473
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