With 4mm slices you will have huge partial voluming in the slice
orientation, what are you trying to do with this data? I would register
your like (i.e. all repetitions of direction 1) gradient orientations and
average them before trying to do eddy current correction if you have low
SNR.
Peace,
Matt.
-----Original Message-----
From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On Behalf
Of Mike Yassa
Sent: Friday, September 18, 2009 6:54 PM
To: [log in to unmask]
Subject: Re: [FSL] volume corruption
Hi Matt,
Can't do 2mm. We're trying to get sub-mm resolution to look at very
small regions. The b value is 1200 on a 3T magnet. I take lots of
averages to get better SNR. The same data worked well for many other
subjects. Is it likely that motion in these few subjects caused this
problem?
Thanks
Mike
On Sep 18, 2009, at 4:08 PM, Matt Glasser wrote:
> That data is probably of too poor quality for the registrations to
> work
> well. I recommend you try 2mm isotropic data, however that SNR
> still seems
> too low to me. Are you using a 1.5T magnet and/or a high b value?
>
> Peace,
>
> Matt.
>
> -----Original Message-----
> From: FSL - FMRIB's Software Library [mailto:[log in to unmask]] On
> Behalf
> Of Mike Yassa
> Sent: Friday, September 18, 2009 4:59 PM
> To: [log in to unmask]
> Subject: Re: [FSL] volume corruption
>
> Hi Matt,
>
> Attached is a picture of the pre-ECC volume. Post ECC is blank as you
> saw in the previous email. The sequence is 0.8 x 0.8 x 4mm coronal
> with 32 directions. The data's dimensions are 256 x 256 x 15 x 34.
> Because of the high resolution they are very noisy, but that's not the
> problem.
>
> Any ideas?
>
> Thanks!
>
> Mike
>
|