Dear Francesca,
Our method cannot reliably segment these thin/faint structures from clinical scans of arbitrary resolution and contrast, which is why they don’t get segmented.
If you want to segment the choroid plexus, you could take then intensities under the ventricles and split them into cerebrospinal fluid and choroid eg with optimal thresholding.
Cheers,
/Eugenio
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Juan Eugenio Iglesias
http://www.jeiglesias.com