Hello, We're trying to make multiple comparisons between FreeSurfer outputs on severely atrophied brains and controls. Some of the comparisons are regions of interest, like hippocampal volume or the volumes of regions in the frontal lobe, but we've also been making comparisons with supratentorialnotvent or supratentorial. Often, the comparisons are consistant - if all the ROIs we're looking at are small then the whole brain volume (supratentorialnotvent) will be significantly smaller as well.
However, there are some cases where the individual regions in the brain do look smaller than the normal cohort, but the supratentorialnotvent looks about average. This makes sense if only a few regions are atrophied, but we've had a few cases where the whole brain is definitely atrophied and the FS assessor definitely looks like it's that way while segmenting the brain, but the supratentorialnotvent volume still looks average. Statistically, the ROI's we're interested in for these cases are two standard deviations below the mean for their age, while the stnv is still about average. When looking through the regions FS has available for us that aren't specific regions we're interested in, they still all look low. How can we explain or understand these situations? It seems like the parts should be close to or equivalent with the whole. Thanks, Washington University in Saint Louis Medical School Radiology Research Assistant Christopher Owen
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