Magnetic resonance (MR) angiography has undergone significant development over the past decade. It has gone from being a novelty application of MR with limited clinical use to replacing catheter angiography in some clinical applications. One of the principal limitations inherent to all MR angiographic techniques is that they remain signal limited when pushed to the limits of higher resolution and short acquisition time. Developments in magnetic gradient hardware, coil design, and pulse sequences now are well optimized for MR angiography obtained at 1.5-T main magnetic field (B-field) strength, with acquisition times and imaging matrix size near their optimal limits, respectively. Recently, the United States Food and Drug Administration (FDA) approved use of clinical magnetic resonance imaging with main magnetic field strengths of up to 4 T. Before FDA approval, use of MR with magnetic field strengths much greater than 1.5 T was essentially reserved for investigational or research applications. The main advantage of high B-field imaging is a significant improvement in the signal-to-noise ratio (SNR), which increases in an approximately linear fashion with field strength in the range of 1.5 to 3.0 T. This increased SNR is directly available when performing MR angiographic acquisitions at higher magnetic field strengths, allowing for better resolution and conspicuity of vessels with similar acquisition times. Little has been reported on the benefits of performing MR angiography at magnetic field strengths >1.5 T. The purpose of this article is to summarize our current experience with intracranial and cervical MR angiographic techniques at 3.0 T.

Initial experience with intracranial and cervical MRA at 3.0T is reported. Phantom measurements (corrected for relaxation effects) show S/N (3.0T) ‫؍‬ 2.14 ؎ 0.08 ؋ S/N (1.5T) in identical-geometry head coils. A 3.0T 3DTOF intracranial imaging protocol with higher-order autoshimming was developed and compared to 1.5T 3DTOF in 12 patients with aneurysms. A comparison by two radiologists showed the 3.0T to be significantly better (P < 0.001) for visualization of the aneurysms. The feasibility of cervical and intracranial contrast enhanced MR angiography (CEMRA) at 3.0T is also examined. The relaxivity of the gadolinium contrast agent decreases by only about 4 -7% when the field strength is increased from 1.5 to 3.0T. Cervical 3.0T CEMRA was obtained in eight patients, two of whom had 1.5T studies available for direct comparison. Image comparison suggests 3.0T to be a favorable field strength for cervical CEMRA. Voxel volumes of 0.62-0.73 mm 3 (not including zero-filling) were readily achieved at 3.0T with the use of a single-channel transmitreceive head or cervical coil, a 25 mL bolus of gadoteridol, and a 3D pulse sequence with a 66% sampling efficiency. This spatial resolution allowed visualization of intracranial aneurysms, carotid dissections, and atherosclerotic disease including ulcerations. Potential drawbacks of 3.0T MRA are increased SAR and T* 2 dephasing compared to 1.5T. Image comparison suggests signal loss due to T* 2 dephasing will not be substantially more problematic than at 1.5T. The 1998 revision of the U.S. Food and Drug Administration guidelines (1) states that MRI systems with main static field strengths of 4.0T and less can qualify as nonsignificant risk devices. Moreover, with the advent of actively shielded magnet technology it is now feasible to site a 3.0T scanner in a clinical setting. Much of the prior use of 3.0T and higher field strength MRI systems, however, has been for pure or clinical research, mostly in the fields of functional brain MRI (e.g., 2,3) and spectroscopy (e.g., 4). This is quite logical, since fMRI and spectroscopy benefit not only from the increased S/N of 3.0T, but also from the linear dependence of magnetic susceptibility changes and chemical shift, respectively.We have applied our 3.0T system to both clinical research and routine clinical use. During the period October 1999 to May 2001, 2908 routine clinical brain exams were performed in an outpatient setting (5). The purpose of this article is twofold: 1) to provide an initial comparison of intracranial 3D time of flight (3DTOF) magnetic resonance angiography (MRA) at 1.5 and 3.0T; and 2) to establish the initial feasibility of 3D contrast-enhanced MR angiography (CEMRA) for the cervical and intracranial arteries at 3.0T. CEMRA is already a well-established technique at 1.5T and has been applied previously to study both intracranial aneurysms (6) and the cervical arteries (7). We examined whether the increased S/N available at 3.0T can translate into increased spatial resolution for CEMRA. We believe that the de...

Initial experience with intracranial and cervical MRA at 3.0T is reported. Phantom measurements (corrected for relaxation effects) show S/N (3.0T) ‫؍‬ 2.14 ؎ 0.08 ؋ S/N (1.5T) in identical-geometry head coils. A 3.0T 3DTOF intracranial imaging protocol with higher-order autoshimming was developed and compared to 1.5T 3DTOF in 12 patients with aneurysms. A comparison by two radiologists showed the 3.0T to be significantly better (P < 0.001) for visualization of the aneurysms. The feasibility of cervical and intracranial contrast enhanced MR angiography (CEMRA) at 3.0T is also examined. The relaxivity of the gadolinium contrast agent decreases by only about 4 -7% when the field strength is increased from 1.5 to 3.0T. Cervical 3.0T CEMRA was obtained in eight patients, two of whom had 1.5T studies available for direct comparison. Image comparison suggests 3.0T to be a favorable field strength for cervical CEMRA. Voxel volumes of 0.62-0.73 mm 3 (not including zero-filling) were readily achieved at 3.0T with the use of a single-channel transmitreceive head or cervical coil, a 25 mL bolus of gadoteridol, and a 3D pulse sequence with a 66% sampling efficiency. This spatial resolution allowed visualization of intracranial aneurysms, carotid dissections, and atherosclerotic disease including ulcerations. Potential drawbacks of 3.0T MRA are increased SAR and T* 2 dephasing compared to 1.5T. Image comparison suggests signal loss due to T* 2 dephasing will not be substantially more problematic than at 1.5T. The 1998 revision of the U.S. Food and Drug Administration guidelines (1) states that MRI systems with main static field strengths of 4.0T and less can qualify as nonsignificant risk devices. Moreover, with the advent of actively shielded magnet technology it is now feasible to site a 3.0T scanner in a clinical setting. Much of the prior use of 3.0T and higher field strength MRI systems, however, has been for pure or clinical research, mostly in the fields of functional brain MRI (e.g., 2,3) and spectroscopy (e.g., 4). This is quite logical, since fMRI and spectroscopy benefit not only from the increased S/N of 3.0T, but also from the linear dependence of magnetic susceptibility changes and chemical shift, respectively.We have applied our 3.0T system to both clinical research and routine clinical use. During the period October 1999 to May 2001, 2908 routine clinical brain exams were performed in an outpatient setting (5). The purpose of this article is twofold: 1) to provide an initial comparison of intracranial 3D time of flight (3DTOF) magnetic resonance angiography (MRA) at 1.5 and 3.0T; and 2) to establish the initial feasibility of 3D contrast-enhanced MR angiography (CEMRA) for the cervical and intracranial arteries at 3.0T. CEMRA is already a well-established technique at 1.5T and has been applied previously to study both intracranial aneurysms (6) and the cervical arteries (7). We examined whether the increased S/N available at 3.0T can translate into increased spatial resolution for CEMRA. We believe that the de...

Most intracranial aneurysms detected by presymptomatic screening in ADPKD patients are small and in the anterior circulation. The follow-up results do not suggest an increased risk for growth and rupture, compared to those of intracranial aneurysms in the general population. These data do not support widespread screening for intracranial aneurysms in the ADPKD population.

Purpose: To determine whether 3.0-T elliptical-centric contrast-enhanced (CE) magnetic resonance (MR) angiography is superior to 3.0-T elliptical-centric time-of-flight (TOF) MR angiography in the detection and characterization of intracranial aneurysms, and to determine whether increasing the acquisition matrix size in 3.0-T CE MR angiography improves image quality. Materials and Methods:A total of 50 consecutive patients referred for MR angiographic evaluation of a known or suspected intracranial aneurysm underwent MR angiography, including three-dimensional TOF and elliptical-centric CE techniques at 3.0 T. The 3.0-T three-dimensional TOF and 3.0-T CE examinations were graded for image quality. A blind review identified the presence and location of aneurysms.Results: A total of 28 aneurysms were identified in 23 of the 50 patients. The 3.0-T TOF MR angiography had a higher mean score for image quality than the 3.0-T elliptical-centric CE MR angiography (P Ͻ 0.0001). A total of 14 patients with aneurysms had conventional angiography for comparison. The 3.0-T TOF showed all the aneurysms, whereas 3.0-T CE MR angiography did not show 1 of 19 aneurysms when conventional angiography was the reference standard. Conclusion:For imaging intracranial aneurysms, 3.0-T TOF MR angiography offers better image quality than 3.0-T CE MR angiography using the elliptical-centric technique.