 |
 |
>From: "Dr. Ahmed Toosy" <[log in to unmask]> >Reply-To: "Dr. Ahmed Toosy" <[log in to unmask]> >To: [log in to unmask] >Subject: small volume correction >Date: Sun, 2 Dec 2001 17:53:40 GMT > >Dear SPM > >I am applying SVC to certain regions using an a priori hypothesis on >uncorrected contrast maps resulting from 2nd level RFX analysis between >patients with optic neuritis and controls (fMRI with visual stimulation). > >I have some questions > >1) Is there a minimum size of SVC that can be applied? If one applies a >small enough SVC then a lot of areas can become 'significantly activated'. I'd like to know the answer too. Firstly, I remember a number--16mm given by Karl in some email.( I am not sure now.) Is this ture? Secondly, Should this size of SVC be relative with the parameters used in smoothing? > >2) After applying an SVC to a particular region of the brain and getting >for example a significant p value, does this mean that I have to ignore all >the other regions of activation in the same map even if some of them are >part of my a priori hypothesis? Also, I am wondering how to show t-map under the condition of SVC. Now I only can get the t-map with uncorrected p-value. Then I get some corrected p-value by using SVC. But I dont know how to get t-map for this region of interest with corrected p-value. > >3) If I want to look at more than one region with SVC can I create a masked >volume by modifying the brainmask template in SPM using something like >MRIcro? Are there other ways of looking for more that one region? > The different VOIs can be analysed separatly? Are they independent for SVC? > >Thanks > > >Ahmed Toosy _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp