Dear SPM community,
I have some questions concerning a 4D quantitative perfusion MRI data
set (ASL; SPM Analyze format). I'm using two occasion of measurements,
each consisting of 40 independent scans (= 4. dimension).
I can import the data into MatLAb via the tool "readanalyze"
(spm_vol/spm_read_vols doesn't work since the array exceeds 3
dimensions). In MatLAb, I want to average over the 40 scans (resulting
in a 3D matrix) as well as over the two occasion of measurements.
Furthermore, I would like to realign, co-register and smooth the images.
So my questions are:
1) Is it allowed to average two images with different scaling factors
(i.e. the two occasion of measurements)? If so, how do I know the
scaling factor of the new (averaged) image?
2) Should the preprocessing procedures be done before averaging over the
40 independent scans and thus be applied to each of the 40 scans?
3) How can I convert the averaged and preprocessed 3D data into SPM
Analyze format while taking care of the correct scaling factor (which is
important for quantitative data)? Spm_write_vol doesn't work since the
new matrix offers no header information.
Best regards,
Michael Hermes
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