Aaron,

I have seen this problem before whereby the signal in the pericallosal artery is enhanced due to inflow artifacts (flow of fully magnetized protons into the imaging slice) which makes the artery indistinguishable from the corpus callosum.  This appears in some pulse sequences and not others, which leads me to believe that the problem can be prevented by using a well-designed 3D T1W sequence.  Unfortunately, there is not much that can be done after the fact other than manually correcting Yuki's output.

Babak