Hi Daniel, I agree, those flip angle differences are quite big and would make a difference to contrast. I suspect gray/white contrast is better for the higher TI and lower flip angles in those scans (and they could benefit from longer TR). So if you have a balanced study/control group it's ok but I wouldn't compare subjects with systematically different protocols like those below.
Cheers, Andre. Bruce Fischl wrote: > Hi Daniel > > those are pretty big differences in flip angle. I'll cc Andre van der > Kouwe on this so he can comment, but I would be hesitant. The increased > TE will have a big effect on dura (darkening it), but will also reduce > gray/white contrast. > > cheers > Bruce > > > On Fri, 17 Aug 2012, Daniel Ferreira wrote: > >> Dear all, >> We are designing a study based on clinical data. We want to work with a >> MPRAGE sequence but subjects have been given 4 different sets of >> parameters: >> >> - TR: 1900; TE: 4,38; TI: 1100; flip angle: 15 >> - TR: 1900; TE: 3,55; TI: 1100; flip angle: 15 >> - TR: 1900; TE: 3,39; TI: 900; flip angle: 9 >> - TR: 1900; TE: 3,39; TI: 900; flip angle: 15 >> >> I wonder how these differences could affect the images and thus the >> results. >> Can I combine all of them or at least some of them? Are they so different >> that I should just study them by separate? >> >> thank you very much on advance >> >> Daniel Ferreira >> >> _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer The information in this e-mail is intended only for the person to whom it is addressed. If you believe this e-mail was sent to you in error and the e-mail contains patient information, please contact the Partners Compliance HelpLine at http://www.partners.org/complianceline . If the e-mail was sent to you in error but does not contain patient information, please contact the sender and properly dispose of the e-mail.
