Listmates,
I'm hoping someone else around here has run into a similar problem with the likelihood of a shared solution. We have a series of Time 1 & Time 2 PD scans that we would like to interrogate for longitudinal tissue changes, but for the time being we are slowed down by issues in the tissue segmentation process. Our PD images have decent resolution with visible differentiation of the grey/white border, but the CSF component is proving troublesome. Standard segmentation (VBM5) yields good grey/white dissociation, but the cortical rim is contaminated by CSF "bleed through" on the grey segments. Also, the ventricles (not the ventricular rims) are lit up and assigned as grey matter. Does anyone have a set of PD tissue priors that he/she could share and/or recommendations on segmentation settings or the like with images of this sequence type?
We have high-res T1 scans at Time 1, but not at Time 2. My thought for these (at least for Time 1) was to coregister and reslice the PD to fit the T1 scan; segment the T1 scan; and apply the grey matter segment as a mask on the PD Time 1 data. But, this still leaves me lost for Time 2, hence some interest in seeing if we can get the PD segments for Time 1 and Time 2 without this complicated (if not questionable) masking scenario.
Regards to all,
Jeff Browndyke
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Dept. of Psychiatry
Duke University Medical Center
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