Hi Shaquanda
> Hi Cyril,
>
> Thanks for the wisdom. That is what I thought, but it is nice to know that is the case. If I may, I have one more questions: Do you know of any references that address the issue of spacial smoothing for irregular volumes (not necessarily an "imaging" reference). I have tried to find this, but have had difficulty.
>
the most popular paper is 'to smooth or not to smooth?' neuroimage 2002;
from there in the ref or using the link in pubmed you'll get other
references
plus the good chapter on
http://documents.wolfram.com/applications/eda/SmoothingDataFillingMissingDataAndNonparametricFitting.html
best
cyril
> Thank you once again very much for your time and thoughts.
> Regards,
> Shaqunada
>
> ----- Original Message ----
> From: cyril pernet <[log in to unmask]>
> To: Shaquanda Jones <[log in to unmask]>; SPM <[log in to unmask]>
> Sent: Monday, November 5, 2007 6:20:58 AM
> Subject: Re: [SPM] Is it appropriate to smooth like this?
>
>
> Hi Shaquanda
>
>> I have heard that when you have a highly non-isotropic scan volume
>>
> that it is appropriate to use a non-isotropic smoothing kernel. Is this
> true?
>
>>
>>
> well I don't know if one can say it is true or not, but spatial
> smoothing will render your data data more normally distributed which is
>
> always good when you want to do some stats .. anyway I have no
> mathematical/statistical explanations here but the usual thing to do is
>
> to smooth 1 to 1.5 times the voxel size for individual data or about 3
> times for group analyses, i.e. if you normalize at 2x2x2 for a group
> analysis, then a 6x6x6 FWHM (or higher) will do - now say you want to
> do
> some individual analyses then for e.g. a non-isotropic 3x3x5 voxel
> size,
> a 4.5x4.5x7.5 FWHM should be ok ..
>
> hope this helps
> cyril
>
>
>
>
>
> __________________________________________________
> Do You Yahoo!?
> Tired of spam? Yahoo! Mail has the best spam protection around
> http://mail.yahoo.com
>
>
>
--
Dr Cyril Pernet,
fMRI Lead Researcher SINAPSE
SFC Brain Imaging Research Center
Department of Clinical Neurosciences
University of Edinburgh
Western General Hospital
Crewe Road
Edinburgh
EH4 2XU
Scotland, UK
[log in to unmask]
tel: +44(0)1315373661
http://www.dcn.ed.ac.uk/bic/
http://www.dcn.ed.ac.uk/bic/sinapse/sinapse.asp
|