The three-dimensional shape analysis of the M1 segment of the middle cerebral artery using MRA at 3T.

INTRODUCTION: The M1 segment of the middle cerebral artery (MCA) is of great importance to neurosurgery and interventional radiology. The purpose of this study was to describe the M1 segment in three dimensions based on shape projection using magnetic resonance angiography (MRA).

METHODS: A three-view method was established and used in the retrospective analysis of 717 M1 segments derived from 3D-TOF MRA images. In this method, the M1 segment was first projected on three orthogonal planes (axial, coronary, and sagittal plane); the courses of the projected vessels were classified as line-shape, C-shape, or S-shape on each orthogonal plane; and then the actual parameters, including internal diameter and so on, were measured on the projected images. The shape classifications and the measured parameters were efficient methods of describing the M1 segment. Twelve geometric models of the vessels were reconstructed and were compared with those from an actual validation method.

RESULTS: The 3D shape of the M1 segment in the 3D orthogonal views was not uniform. Only 17.3 % M1 segments were straight, 43.5 % followed plane curves, and nearly 40 % were tortuous in 3D space. The probability distributions of shape classifications changed with age. The proportion of the tortuous vessels increased with age. We also showed that the three-view method is effective with a volume relative error of less than 13 %.

CONCLUSION: The three-view method is convenient for describing the 3D morphology, including the shape information, of the M1 segment. It is a potential method for planning and predicting risk in neurosurgery/neurointervention.