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Great, thank you so much for these suggestions!! Much appreciated! Best wishes, Sven On Thu, Jul 27, 2017 at 11:51 AM, John Ashburner <[log in to unmask]> wrote: > The best thing I can think of is that you can average the two images to > achieve better signal to noise. They would need registering together first > though. Probably the most accurate approach for rigid-body alignment of > such data using SPM12 would involve using the Longitudinal toolbox. You > can make it do within-modality rigid alignment by setting the warping > regularisation to [Inf Inf Inf Inf Inf]. For this, it doesn't matter what > time intervals you specify, as these only enter into the nonlinear warping > part. > > One of the outputs should be a weighted average of the two aligned > images. One thing to watch out for is that this average is bigger than the > original images, and it will contain some regions where there is missing > data. These regions can potentially interfere with other processing steps. > > I can't comment so much on interesting questions to ask of the data. In > regards to quality of combined 1.5T versus 3T, this will depend on the > imaging sequences used. Without further software development related to > correcting the additional artifacts in 3T data, I suspect that you may > actually get more out of group comparisons using 1.5T data. > > Best regards, > -John > > > > On 26 July 2017 at 18:11, Sven Mueller <[log in to unmask]> wrote: > >> Dear SPMers, >> >> for some reason (without going into the details) I find myself with the >> luxury of having 2 back-to-back acquired (in one session) structural scans >> (MPRAGES) on a 1.5T scanner. Our study sample was comprised of 4 different >> groups (2 patient, 2 control). I am now wondering how to exploit this >> unusual situation. We used the ADNI protocol and they suggest that one >> option could be to combine both images (after spatial registration) and >> thus increase SNR. Thus, one option would be to do this and then conduct a >> VBM analysis and simply compare the 4 groups. But, one silly question, are >> 2 combined 1.5T as good (or better) than one 3T scan? >> >> However, I am wondering if people out there also have some other >> ideas/suggestions. I thought of using one of the two scans, do the VBM and >> then use it to see whether we can predict which group the person belongs to >> in the second anatomical. I have seen papers do this functionally so I have >> no idea whether this approach would make sense for structural analysis or >> not and would appreciate any advice on this. Third, are there other >> options/possibilities of what could be done with such data? >> >> Many thanks in advance for any suggestions, >> >> Sven >> > >