Dear Volkmar,
I'm not quite agree with you in that " Correlating this with arbitrary
unlimited scores will not give meaningful results". I think since FA
changes can be indicative of fiber maturation process, including
myelination. Correlation of FA and cognitive scores could support the
importance of intact fiber for the proper operation of cognitive
function.
Best Wishes!
Sincerely yours,
Deqiang Qiu
Department of Diagnostic Radiology
The University of Hong Kong
Rm 406,Blk K,
Queen Mary Hospital
Pokfulam Road,
Hong Kong
Tel: (+852) 28553307
Fax: (+852) 28551652
-----Original Message-----
From: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]]
On Behalf Of Volkmar Glauche
Sent: 2006Äê8ÔÂ1ÈÕ 0:34
To: [log in to unmask]
Subject: Re: [SPM] In need of DTI help
Dear Jessica,
do I understand you correctly that you have 3 different behavioural
scores
per subject and want to find whether there are areas in FA maps of a
group of subjects where anisotropy changes in relation to the behaviour
scores? If so, yes this is technically possible with SPM - however you
need to consider that FA is a quantity limited to a range between 0 and
1.
Correlating this with arbitrary unlimited scores will not give
meaningful results, but you should be fine with e.g. percent-range
scores.
Volkmar
On Mon, 31 Jul 2006, <Jessica> <Galgano> wrote:
> Hello SPM experts!
>
> I am in desperate need of some help. If you have 3 different
> cognitive scores that were
> measured from 3 different cognitive tasks, can you then correlate
> these scores with each pixel's FA value (DTI output) in the DTI
> brain map? Could this be done using only SPM? If so, can someone
> explain how?
>
> Thank you!
> Jessica, NY
>
> "Voxel-based correlational analysis. For each slice position,
> analysis of the DTI data produces mean diffusivity, FA, and T2-
> weighted images, which are identical in anatomic position. The
> first step in image processing involved stripping of the skull and
> dura using an automated algorithm22 (Brain Extraction Tool; Oxford
> Centre for Functional Magnetic Resonance Imaging of the
> Brain; http://www.fmrib.ox.ac.uk/fsl/bet/index.html). For each
> subject,
> the T2-weighted images were then fitted to a symmetric
> echo-planar MRI brain template using a 12-parameter, affine
> normalization
> algorithm from Statistical Parametric Mapping23 (SPM
> 99, Functional Imaging Laboratory, Institute of Neurology,
> University
> College London, UK; http//www.fil.ion.ucl.ac.uk/spm). A
> symmetric echo-planar template was used. An identical transformation
> was then applied to the mean diffusivity and FA images.
> This was repeated for all subjects so that a full set of DT images
> was produced, all fitted to an identical template. All of the
> normalized
> images were reviewed visually to ensure that there were
> no obvious registration errors. The normalized images were then
> smoothed using an isotropic Gaussian filter (full width half maximum
> 4 mm). This process reduces the impact of small errors in
> registration by recalculating the intensity at each voxel based on a
> weighted mean of intensity at that voxel and surrounding voxels."
>
>
--
Volkmar Glauche
-
Department of Neurology [log in to unmask]
Universitaetsklinikum Freiburg Phone 49(0)761-270-5331
Breisacher Str. 64 Fax 49(0)761-270-5416
79106 Freiburg
|