To TOF or not to TOF: strategies for non-contrast-enhanced intracranial MRA at 7 T

Object The purpose of this study was to optimize and to evaluate 3D time-of-flight (TOF)-like non-contrast enhanced MR-angiography (MRA) techniques for display of the intracranial vessels on a 7 T whole-body scanner. Materials and methods Three different gradient echo sequences (TOF, VIBE, MPRAGE) were compared in 12 healthy volunteers and 13 patients. Two blinded senior radiologists independently rated the presence or absence of artefacts and the conspicuity of ten different vessel segments in source and maximum-intensity-projection (MIP) images. Results In source images, MPRAGE achieved the best results; even the fine vessels and the vessels near the air-containing mastoid were depicted very well. Intraluminal signal loss, which was a problem in the greater vessels in TOF and VIBE imaging, was less pronounced in MPRAGE images. In the MIP images, TOF performed best. Both VIBE and MPRAGE can generate TOF-like contrast and cover the whole brain in less than 15 min, whereas TOF covered only a subvolume of the brain. Conclusion MPRAGE performed especially well in this 7 T imaging study. The accuracy of the sequence deserves further evaluation in patients with vessel stenoses and aneurysms.