Dear FSLers:<br>I use FDT on my DTI data , and it goes smoothly . However , I have two questions about the DTIFIT and data . <br>First , I am wondering the relationship between S0 image generated by&nbsp; &quot;dtifit&quot; and the non diffusion weighted images . In the Toolbox of dtifit , the output , S0 , is described as &quot;raw T2 signal with no diffusion weighting &quot; ,but I find something wrong&nbsp; in my experiment .
<br>I have 3 no diffusion weighted images and some diffusion weighted images. I eddy correct them using the first image (b=0) as the reference .Then I input all of them into &quot;dtifit&quot; , I find the S0 (output)&nbsp; is neither equal with any one of b=0 , or equal with average of them . When I input only one b=0 , the S0 is different with input obviously . I am sure that the bvecs and bvals is correct .
<br>Second , does FDT defines that one direction must match only one image ? My data has 12 (+1) diffusional directions , but for some reasons I don`t konw , one subject&nbsp; is sampled 3 times in the 12 (+1) directions . It means the raw data of one subject have 13*3=39 volumes in 12(+1) directions . In this occasion , may I take the 39 volumes as samples in different 39 directions and bvecs ( bvals ) are repeated three times ? Is it allowed by DTIFIT&nbsp; ? If not , how should I do ?
<br><br>Thank you for your reply !<br><br>Yujin Zhang <br>graduate student<br>State Key laboratory of Cognitive Neuroscience and Learning<br>Beijing , China<br>