Time-of-Flight Magnetic Resonance Angiography at 7 Tesla

Abstract

Magnetic resonance angiography (MRA) is noninvasive and does not require the application of high doses of contrast agents, and thus is used in the clinical routine for evaluation of cerebrovascular diseases, eg, aneurysm and arteriovenous malformations. However, more subtle microvascular disease usually cannot be seen with the resolution capabilities of standard field strength MRA. The purpose of this study was to evaluate the ability of 7-T time-of-flight (ToF) MRA to depict the arterial brain vasculature and to compare the results to data from 1.5 T and 3 T. The study was IRB approved and complied with The Health Insurance Portability and Accountability Act. All subjects gave written informed consent. Eight healthy volunteers (age: 36 +/- 10 years; 3 female, 5 male) were investigated using ToF MRA at 7 T, 3 T, and 1.5 T. Signal intensities of the large, primary vessels of the Circle of Willis were measured and signal-to-noise ratios were calculated. Visibility of smaller arteries was evaluated. The results show that ultrahigh field allows depiction of the large vessels of the Circle of Willis. Although it provides only small increases in signal-to-noise ratios for these vessels, compared with 1.5 T and 3 T, it additionally demonstrates considerably more first- and second-order branches. Because of its considerably enhanced potential to depict vessels of the Circle of Willis and its first- and second-order branches, ToF MRA at 7 T may become an important tool in future neuroradiology research and clinical care.