Hi Johannes,
Basically i am more interested in the basal ganglia, and getting a
high spatial resolution in the least amount of time. With AP foldover
i have to set a FOV which i think is a bit too high -- you scan alot
of air to the front and back of the skull. With RL, i can lower the
FOV without worries about noses... The ears are still inside the FOV,
so i can have a higher resolution in the same amount of time.
I was wondering if RL is sometimes also used for fMRI, or if it's
almost never used, or if there is no preference for either way.
Cheers,
johan
On 12/18/06, Johannes Klein <[log in to unmask]> wrote:
> 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
> >
> >
> >
>
--
J.(Johan) N. van der Meer
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