Evaluation of Intracranial Aneurysms with 7T versus 1.5T Time-of-Flight MR Angiography - Initial Experience

Purpose: The purpose of this study was to compare the depiction of intracranial aneurysms by 3D time-of-flight (TOF) magnetic resonance angiography (MRA) at 7 Tesla (T) with the clinical standard TOF MRA at 1.5 T and with digital subtraction angiography (DSA). Materials and Methods: 7T and 1.5T TOF MRA images optimized for both field strengths were compared in ten patients with an unruptured intracranial aneurysm. Two blinded neuroradiologists independently rated the image quality of the dome, the neck, and the vessel of origin of all aneurysms in MRA source and maximum intensity projection (MIP) images. DSA was obtained in all subjects and served as reference standard. The mean values of image quality were compared by Wilcoxon signed rank test. In all patients the number and location of the aneurysms was confirmed by DSA. Results: Both readers identified twelve aneurysms in ten patients in 7T, 1.5T TOF MRA and DSA. The image quality of the aneurysm dome was rated higher in 8 of 12 aneurysms and the image quality of the aneurysm neck was superior in 9 of 12 aneurysms at 7T TOF MRA compared to 1.5T TOF MRA. The depiction of the parent vessel was graded almost equally by both readers. Conclusion: Our initial results indicate that image quality of intracranial aneurysms may benefit from the increased spatial resolution of 7T TOF MRA compared with 1.5T TOF MRA. Tailored scan protocols and optimized radiofrequency head coils are needed to further improve the image quality of 7T TOF MRA.