Hi SPM experts,
I wanted to expand upon a previous post in which I asked about the differences between "New Segment" and "Estimate and Write" as it pertains to a custom-template DARTEL VBM analysis.
I have a sample population of n=132 roughly evenly distributed between control and experimental subjects. I ran two VBM-DARTEL pipelines, with age as a covariate, both on the SAME population:
1) "New Segment," followed by "Run DARTEL (create Template)," followed by "Normalize to MNI Space" (with 8mm smoothing)
- This is based on John Ashburner's 2010 tutorial.
2) "VBM8: Estimate & Write," followed by "Run DARTEL (create Template)," followed by "VBM8: Write already estimated segmentations," followed by an 8mm smoothing.
- This is based on the VBM8 manual.
The results, attached, are vastly different. Does anyone have insight into this? Is there an obvious error in my methods? My understanding is that pipeline (2) is based on New Segment, so the results should be very similar, correct? Pipeline (1) takes about 20hrs, while pipeline (2) takes about 40 hrs.
Thank you in advance for your help,
Michael Regner, MD
University of Colorado School of Medicine
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