Rofo 2008; 180 - A22
DOI: 10.1055/s-2008-1052583

To TOF or Not to TOF: Non-contrast-enhanced intracranial MRA at 7 Tesla

S Maderwald 1, 2, SC Ladd 1, 2, ER Gizewski 1, 2, O Kraff 1, 2, JM Theysohn 1, 2, K Wicklow 3, C Moenninghoff 1, 2, I Wanke 1, 2, ME Ladd 1, 2, HH Quick 1, 2
  • 1Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany
  • 2Dept. of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany
  • 3Siemens Medical Solutions, Erlangen, Germany

Purpose: 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 arteries at 7T.

Fig.1: Rating of large vessels (ML P1. and A1) and small vessels (M3, P3. and A3) for the four different sequence types. average grade of the two readers. Significant differences in ratings between source and MIP images were found in large vessel VIBE(p<0.01), small vessel VIBE (p<0.001) as well as small and large vessel MPRAGE (p<0.001). * indicates p<0.05.

Materials and Methods: Three different gradient echo sequences (TOF, VIBE, MPRAGE) were compared in 12 healthy volunteers and 13 patients on a Magnetom 7T whole-body scanner (Siemens Erlangen, Germany). Image acquisition was performed with two different radiofrequency transmit/receive head coils: 1) a quadrature birdcage head coil (Invivo Diagnostic Imaging Corp., Gainesville, FL, USA) was used for imaging the first 8 volunteers and 2 patients; 2) an 8-channel head coil (Rapid Biomedical GmbH, Würzburg, Germany) was used for the remaining 4 volunteers and 11 patients. Two blinded senior radiologists independently rated the presence or absence of artefacts and the conspicuity of 10 different vessel segments in source and maximum-intensity-projection (MIP) images.

Results: In source images, MPRAGE achieved the best results; even the fine vessels (Fig.1) 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, were less pronounced in MPRAGE images. In the MIP images, TOF performed best.

Conclusion: Both VIBE and MPRAGE can generate TOF-like contrast and cover the whole brain in less than 15 minutes, whereas TOF covered only a subvolume of the brain. MPRAGE performed especially well in this 7 Tesla imaging study. The accuracy of the sequences deserves further evaluation in patients with vessel stenoses and aneurysms.