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Hi Johan, In short, it depends on what structures you're interested in. If you're trying to image oritofrontal or frontopolar function, AP may not be a good idea. AP has the advantage of retaining a symmetric looking brain, but the distortions are just as bad as with RL. Unwarping generally helps to aleviate registration problems and to improve "visual appeal", but bear in mind that it cannot account for signal build-up in "squashed" areas of the brain. If you're interested in cerebellum, take a look at both AP and RL encoded images, and see if the mastoids give you trouble in either direction. Also, you may want to acquire oblique planes to sort your folding problem. If you're doing DTI rather than fMRI, you will probably have to adjust your bvecs accordingly though, so I don't know if angulating your planes is an option for you. Cheers, Johannes Johan schrieb: > I got a question on scanner parameters... the option where you can > choose your phase-encode direction. > > With AP, the brain is not distorted along the RL direction, but you > have to set a fairly high FOV of 220 mm (and get lower resolution), > otherwise the nose will stick into the cerebellum. > > With RL, you can set a smaller field of view (and thus obtain higher > resolution), but your images will be warped in RL and therefore not be > very symmetrical... > > Can RL foldover be used... or is that generally a bad idea (and why)? > > Cheers, > johan > > >