Dear FreeSurfer Experts,

I want to compare structural measures(eg. thickness) between patients and controls controling for the effects of age, gender and scanner (parts of sample were scanned in scanner 1 parts in scanner 2).

I want to answer the question: do patients and controls differ significantly in lGI when controlling for age (continous variable), gender(male/female), scanner(scanner1/scanner2)?

so i have to categorical (gender, scanner) and one continous variable to control for.

my FSGD file looks like:

GroupDescriptorFile 1               
Class PatientFemaleScanner1
Class PatientFemaleScanner2
Class PatientMaleScanner1
Class PatientMaleScanner2
Class ControlFemaleScanner1
Class ControlFemaleScanner2
Class ControlMaleScanner1
Class ControlMaleScanner2
Variables Age
Input    subject1    ControlMaleScanner1    23.6
Input    subject2    ControlFemaleScanner2    37.7
Input    subject3   PatientFemaleScanner1    32.6

...

Total I would have 16 regressors with following contrasts:

first conrast: is there a difference in structural measure(eg. thickness) between patients and controls controlling for gender, scanner, age?

0.25 0.25 0.25 0.25 -0.25 -0.25 -0.25 -0.25 0 0 0 0 0 0 0 0

second contrast: is there a difference between the two scanners scanner 1 and 2 controlling for effects of gender, age and group?

0.25 -0.25 0.25 -0.25 0.25 -0.25 0.25 -0.25 0 0 0 0 0 0 0 0

Questions:

• Are the Contrasts created ok?
  
• How could I control better for the effect of scanner, as part of the sample was scanned with scanner 1 another part with scanner 2?

Thank you very much for your help!

Geo

-- 
Oana Georgiana Rus
PhD Student
Neuroimaging Center TUM-NIC
Klinikum rechts der Isar
Technische Universität München
Einsteinstr.1
81675 München
Raum 5.8

Tel. 089 4140 7971