Dear Afni people,
I have been using AFNI quite successfully in PET data pre-processing. In order to streamline my pipeline I was hoping to use the Dimon program for dicom organization and volume construction which would allow me to omit a volume construction step with SPM.
My PET data are 3D+time datasets in which the spatial distribution of numeric values of individual voxels changes massively over time. I realize that most AFNI programs are highly optimzed for EPI datasets, however apart from volume reconstruction I haven’t been running into any troubles.
So what happens is that Dimon appears to apply some kind of within slice and probably also across volume normalization on numeric values of voxels perturbing the PET data timeline for individual voxels. In short overall numeric values of voxels differ from what is found in the raw data with the effect being exaggerated in later time points where certain regions are supposed to display higher radioactive decay count-rates (i.e. the numeric value of the voxels) than other brain regions.
I couldn’t find any information on normalization of numeric values of voxels in the Dimon documentation and was wondering if it was possible switch off the feature in order to make Dimon applicable for this kind of data. I have as yet not been able to find a flag controlling this behavious.
I have attached screenshots of an individual PET image which was constructed with Dimon as well as SPM.
Thank you, Ulrich Sauerzopf