Dear Lorena,
I agree with Chris Watson, who answered your original email.
It is very, very difficult to mix different scanners and different field strengths and in general we would advise against it as there are likely to be many non-biological factors that could result in changes that you would detect.
If you really want to combine things then I would do independent analyses for the two different datasets and then combine the results, either qualitatively or quantitatively, as having similar results on different scanners is quite compelling. It also avoids the minefield of comparing changes in the data that could be attributable to the scanners only, as all your comparisons, to generate the individual statistical results, would be done on within-scanner data.
Sorry I don't have better news.
All the best,
Mark
On 17 Jan 2013, at 19:31, Lorena Jimenez-Castro <[log in to unmask]> wrote:
> Dears FSL users and experts,
>
> I am re-posting my question since I am hoping you experts may provide me with some insights into this matter. So, any advice and brief explanation would be greatly appreciated!
>
> We are going to recruit participants from two different countries, in both sites we will be recruiting healthy subjects and patients and we will be performing DTI and resting state fMRI using the same acquisition parameters on all of the subject in each site. However in one country we have a 1.5 tesla scanner and in the other country we have a 3.0 tesla and the scanners are from different manufacturers in each site.
>
> At the end we would like to combine the data from the two countries (the DTI as well as the fMRI data).
>
> if we use different scanners, which have different magnetic field strength (tesla) and manufacturers, Is it possible to combine the data?
>
> Thanks,
>
> Lorena
>
> -- Lorena Jimenez-Castro, MD
> Postdoctoral Fellow
> Research Imaging Institute
> University of Texas Health Science Center
> 8403 Floyd Curl Drive
> San Antonio, TX 78229
> (210) 567-8215- office phone
> (210) 567-8103- fax
>
>
>
>
> _____________________________________________________
> Subject: combine data from two different scanners with different tesla.
>
> From: Lorena Jimenez-Castro <[log in to unmask]>
>
> Reply-To: FSL - FMRIB's Software Library <[log in to unmask]>
>
> Date: Wed, 16 Jan 2013 23:40:42 +0000
>
> Dear FSL users,
>
> We are going to submit a grant and We want to make sure that what we are doing is fine. This is the question: We are going to recruit participant from two different countries, in both sites we will be recruiting healthy subjects and patients and we will be performing DTI and resting state fMRI using the same parameters on all of the subject in each site. However in one country we have a 1.5 tesla scanner and in the other country we have a 3.0 tesla and the scanners are from different manufacturers. At the end we would like to combine the data (DTI and fMRI) from the two countries.
>
> if we use different scanners, which have different magnetic field strength (tesla) and manufacturers, Is it possible to combine the data?
>
> Thank you very much
>
> Lorena
|