Dear Marko, List,
I have a script (a function, actually) for simply calculating the SD, mean and
SD/Mean images of a time series, without nowing for sure if the latter is the
best measure to look at. See attachment. I'd be interested to hear other
opinions!
Cheers,
Bas
--------------------------------------------
Dr. S.F.W. Neggers
dept. of Psychonomics,Helmholtz Institute
Utrecht University
Heidelberglaan 2
3584 CS, Utrecht, room 17.09
the Netherlands
Tel: (+31) 30 253 4582 Fax: (+31) 30 2534511
E-mail: [log in to unmask]
Web: http://www.fss.uu.nl/psn/pionier
--------------------------------------------
Op donderdag 9 juni 2005 10:00, schreef u:
> Hi Bas,
>
> > I also have a (probably naive) question regarding the SNR measures
> > described by Peter Kingsley in his email (just re-read it) as well. When
> > I understand his post well, this classical type of SNR is for noise over
> > voxels within a single MR image. This might be interesting for anatomical
> > images. For fMRI though, I'd say it is much more interesting to now
> > something about singal-noise relation ships in time instead of in space,
> > i.e. random variations in time with respect to mean signal in time, or
> > even better, task-rest related amplitudes with respect to noise.
>
> An excellent point, thanks for making it!
>
> > SNR i sometimes simply divide mean signal (over time!) of a voxel or of
> > the average time signal of bunch of voxels in an ROI, and divide it
> > through the SD (over time!). One can then make an SNR image when doing
> > this for each voxel. For functional imaging that is much more informative
> > i'd say.
>
> ... hm.. sounds like a nice apporach. Did you script this? I would like
> to take a look at it.
>
> > definitely are better measures for detectability of a signal based on SNR
> > measures at rest, I would also be interested in hearing about them (and
> > I'll dive deep into Medline of course). Perhaps we could explore posters
> > on fMRI-SNR measures next week in Toronto at the HBM together ;-)
>
> Shame, I won't be there ;) But enjoy anyway, Toronto is great!
> Best,
> Marko
--
|