Hi,
You need to load in a 2D gradient-echo scan. You can acquire a double-echo
scan, but that can lead to large phase ramps across the image. It might be
better to acquire two single images with difference echo times, the
difference should be a multiple of the time to bring water/fat in phase.
If you are acquiring with a quadrature head or body coil you need to set the
cv rhrcctrl to 3 to get magnitude & phase, or 12 to get real and imaginary.
Phase values range from -1000pi ->0 -> +1000pi as integers.
If you are using an array coil to receive, there are two options. In both
cases set rhrcctrl as above. You can then set saveinter = 1 which will save
images for every coil in the receive array. For the 8 channel head coil,
you'll get 18 images per slice (8coils*two images per coil + 2 sum of
squares images). The sum of squares images can be discarded. You can then
calculate the phase differences between each echo time for each coil, and
combine them into one phase image.
An alternative suggested by a previous poster was to turn ASSET on, then set
the asset_factor = 1. The coil phases should then be correctly combined.
On 19/12/07 18:22, "Evangelou, Iordanis (NIH/NINDS) [F]"
<[log in to unmask]> wrote:
> Does anyone have any experience with General Electric Signa Phase Maps?
>
> How can we acquire them?
>
> Thanks
>
> -------------------------------------------------------
> Iordanis E. Evangelou, DPhil
> Postdoctoral Fellow
> Neuroimmunology Branch
> National Institute of Neurological Disorders and Stroke
> National Institutes of Health
> Bethesda, MD 20892
> -------------------------------------------------------
>
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