Main anatomical features of the M1 segment of the middle cerebral artery: a 3D time-of-flight magnetic resonance angiography at 3 T study.

The purpose of our study was to determine the main anatomical features of the M1 segment of middle cerebral artery (MRA) using a 3D TOF-MRA at 3 T. Reconstructed and post-processed MRA images were independently analysed by two anatomists in order to determine the course patterns, the division patterns and the early cortical branches patterns of the M1 segments. The division patterns were defined as bipode, tripode or other. The ECB were studied according to their number and their distance from the origin of the M1 segment. The interobserver agreement, to determine the division patterns of the M1 segment, was calculated. The division of the M1 segment was bipode in 73% of the MCAs, monopode in 17%, tripode in 9%, and fan-shaped in 1. In 46% of the cases no ECB was found. In the other cases, only 1 ECB was found and it arose from the medium part of the M1 segment. Our results confirm post-mortem microdissection studies and show that strict anatomical criteria may be applied to 3D TOF MRA at 3 T.