Dear all,

in the applytopup-posts it was suggested to rather use the "Free mode" for DTI protocols in Siemens scanners instead of MDDW. I also thought about this and searched the internet without luck. Can someone tell me, what needs to be taken into account, when creating a set of diffusion directions? Is there a page that lists example protocols / direction settings - or is it that everybody does it differently?

I also have a question about blip up / blip down scanning. It seems to me that I have to scan the sequence twice in opposite readout directions, meaning that I have a (minimal) chance of screwing up the positioning of the second dataset. So, is it be possible to create a "free mode" direction set with two sets of directions with opposite values or are readout-direction and dw-directions two totally different pair of shoes (showing my lack of basic MR physics). Also: are the eddy current distortions different not only for the readout direction but also for the variable gradient directions? Or could I also scan a couple of b0-images in AP and PA direction (saving some scanning time)?

As always, thank you for your help.

Martin