Purpose: To compare standard and high spatial resolution intracranial 3D time-of-flight (TOF) MR angiography at 3.0T with 1.5T.
Methods and Materials: In a prospective, intraindividual study MR angiography (3D TOF MRA) of the circle of Willis was performed in eight patients and seven volunteers both on a 1.5-T and 3.0T MR system (Intera, Philips Medical Systems, NL). In the standard protocol (st 3D TOF), an image matrix of 336 x 213 on 160 mm FOV was used both on 1.5T and 3.0T yielding a non-zerofilled voxel size of 0.48 x 0.75 x 2.00 mm3 (0.92 mm3), respectively. In addition, according to the signal gain, a high spatial resolution 3D TOF MR protocol (hr 3D TOF) was used at 3.0T with a matrix of 832 x 568 on 250 mm FOV (non-zerofilled voxel size: 0.30 x 0.44 x 1.00 mm3 (0.13 mm3)). Overall image quality of the angiograms was assessed on a 5-point scale (5=excellent through 1= nondiagnostic) and depiction of small vessel segments and vascular pathologies was graded (3=ecxellent through 0=not visible) by two experienced readers.
Results: Hr 3D TOF at 3.0T was judged to provide the best image quality (mean score: 4.53) with significantly better grades as compared to st 3D TOF at 3.0T (mean score: 3.13; p < 0.001) and st 3D TOF at 1.5T (mean score: 2.20; p < 0.001). At hr 3T TOF depiction of small vessel segments and vascular pathologies were significantly better as compared to both st 1.5T and st 3T TOF (p < 0.01, respectively).
Conclusion: Intracranial 3D TOF angiography at 3.0T offers better image quality, better depiction of vessel segments and improved depiction of vascular pathologies as compared to 1.5T. The signal gain at 3.0T provides diagnostic improvement in studies of cerebrovascular disease.