Morphologist - Symmetric atlas to reduce bias?
Posted: Mon Nov 30, 2020 4:42 pm
Dear colleagues,
I'm interested in using BrainVISA's Morpohologist pipeline to study the hemispheric asymmetry in the length of the Sylvian Fissure, which displays a population-wide asymmetry towards the left hemisphere. As a test, I first entered the original T1-anatomy images of participants as well as their left-right mirrored versions into the pipeline, expecting the reconstructed Sylvian fissure to reverse as well. However, I found that the Sylvian fissure length of the original and left-right flipped brains had the same - usual leftward - asymmetry, albeit that the degree of asymmetry was weaker for the artificially flipped brains. I visually checked all reconstructed fissures to make sure this was not due to differences in the labelling of segments between the original and flipped brain. In doing so, I noticed that the overall shape of the Sylvian Fissure likewise did show the dramatic reversal I expected in the left-right mirrored brains. I believe this may be indicative of bias, which I think most likely originates from the asymmetry inherent to the BrainVisa sulcus atlas. I was wondering if simply using a symmetrical version of the default sulcus atlas would fix the issue and, if so, how can I use such an atlas within the morphologist pipeline? If not, what additional/other steps should I take?
I'm interested in using BrainVISA's Morpohologist pipeline to study the hemispheric asymmetry in the length of the Sylvian Fissure, which displays a population-wide asymmetry towards the left hemisphere. As a test, I first entered the original T1-anatomy images of participants as well as their left-right mirrored versions into the pipeline, expecting the reconstructed Sylvian fissure to reverse as well. However, I found that the Sylvian fissure length of the original and left-right flipped brains had the same - usual leftward - asymmetry, albeit that the degree of asymmetry was weaker for the artificially flipped brains. I visually checked all reconstructed fissures to make sure this was not due to differences in the labelling of segments between the original and flipped brain. In doing so, I noticed that the overall shape of the Sylvian Fissure likewise did show the dramatic reversal I expected in the left-right mirrored brains. I believe this may be indicative of bias, which I think most likely originates from the asymmetry inherent to the BrainVisa sulcus atlas. I was wondering if simply using a symmetrical version of the default sulcus atlas would fix the issue and, if so, how can I use such an atlas within the morphologist pipeline? If not, what additional/other steps should I take?