Magnetic Resonance Angiography at 3.0 Tesla: Initial Clinical Experience

Abstract

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.

Dynamic pulmonary perfusion and flow quantification with MR imaging, 3.0T vs. 1.5T: Initial results

“…The main advantage of MRI at 3.0T is the SNR gain that scales linearly with field strength (23,24). Furthermore, it can be used flexibly to reduce acquisition time, improve spatial resolution, or both (24 -26).…”

“…In addition, the background noise is reduced at 3.0T because of the shortening of T2*, result in better discrimination of vascular segments. These theoretical advantages of 3.0T imaging may enhance the performance of pulmonary time-resolved MRA, in which SNR can be limiting at 1.5T (23,24,27).…”

Imaging artifacts at 3.0T

“…Because the T1 of the unenhanced tissue typically increases more than the enhancing tissue, equivalent doses of Gd chelate often produce a greater effect at 3T than at 1.5T. This is greatly advantageous for MR angiography (MRA) (18,19,21), and has been used to reduce the contrast agent dose at 3T (32). At equivalent doses, however, increased dural enhancement is normal and should not be interpreted as a sign of a disease process, such as meningitis (Fig.…”

Intracranial contrast‐enhanced magnetic resonance venography with 6.4‐fold sensitivity encoding at 1.5 and 3.0 Tesla

“…SENSE can, however, suffer from a loss in signal-to-noise ratio (SNR) that is due to both the reduction in Fourier samples and the g-factors associated with the coil array used in data acquisition (13). In high spatial resolution MR angiography (MRA) at 1.5T, this SNR loss can lead to poor vascular detail in small vessels (15,16), and has limited 1D-SENSE accelerations to typically less than four in clinical applications. The purpose of this prospective study was to compare identical SENSE-accelerated 3D CE-MRV acquisitions at 1.5T and 3.0T on the basis of vessel conspicuity and diagnostic image quality.…”