High-Resolution Postcontrast Time-of-Flight MR Angiography of Intracranial Perforators at 7.0 Tesla

Abstract

Background and PurposeDifferent studies already demonstrated the benefits of 7T for precontrast TOF-MRA in the visualization of intracranial small vessels. The aim of this study was to assess the performance of high-resolution 7T TOF-MRA after the administration of a gadolinium-based contrast agent in visualizing intracranial perforating arteries.Materials and MethodsTen consecutive patients (7 male; mean age, 50.4 ± 9.9 years) who received TOF-MRA at 7T after contrast administration were retrospectively included in this study. Intracranial perforating arteries, branching from the parent arteries of the circle of Willis, were identified on all TOF-MRA images. Provided a TOF-MRA before contrast administration was present, a direct comparison between pre- and postcontrast TOF-MRA was made.ResultsIt was possible to visualize intracranial perforating arteries branching off from the entire circle of Willis, and their proximal branches. The posterior cerebral artery (P1 and proximal segment of P2) appeared to have the largest number of visible perforating branches (mean of 5.1 in each patient, with a range of 2–7). The basilar artery and middle cerebral artery (M1 and proximal segment M2) followed with a mean number of 5.0 and 3.5 visible perforating branches (range of 1–9 and 1–8, respectively). Venous contamination in the postcontrast scans sometimes made it difficult to discern the arterial or venous nature of a vessel.ConclusionHigh-resolution postcontrast TOF-MRA at 7T was able to visualize multiple intracranial perforators branching off from various parts of the circle of Willis and proximal intracranial arteries. Although confirmation in a larger study is needed, the administration of a contrast agent for high-resolution TOF-MRA at 7T seems to enable a better visualization of the distal segment of certain intracranial perforators.

Non-moyamoya vessel network formation along steno-occlusive middle cerebral artery

“…However, using ultra-high field 7T MRI, numerous microvessels invisible by conventional MRA (1.5T or 3T) have been revealed around steno-occlusive MCAs. 20,21 These microvessels are comparable with the findings of DTFV on HRMRI. A similar phenomenon was also reported in coronary atherosclerosis, 22,23 which is supposed to be triggered by chronic hypoxia/ischemia.…”

Clinical vascular imaging in the brain at 7 T

“…Compared to 1.5 T and 3 T, arterial TOF MRA at 7 T allows the visualization of much smaller intracranial arteries, such as the lenticulostriate arteries ( Fig. 2 ), while adding a contrast agent may enable the visualization of even more distal arteries in addition to veins and venules ( Harteveld et al, 2015 ; Madai et al, 2012 ; Kang et al, 2010 ). The presence of intracranial arterial narrowing alone, however, does not necessarily correspond to a stroke origin; arterial stenosis may already have been present a long time before the onset of stroke, and may be compensated by adequate primary (circle of Willis) or secondary (leptomeningeal) collaterals ( Liebeskind et al, 2011 ; Hartkamp et al, 2016) .…”

“…By enabling the evaluation of the brain parenchyma on a submillimeter scale, very small cerebrovascular lesions, such as cortical microinfarcts, have come within the detection limit of 7 T and to a lesser degree 3 T MRI ( van Dalen et al, 2015) . Also, compared to 1.5 T arterial MR angiography (MRA), the use of high-field (3 T) and even more so ultra-high field MRI (7 T), has enabled the visualization of the lumen of much more peripheral intracranial vessels, and of the intracranial vessel walls of the circle of Willis (CoW) and beyond ( Harteveld et al, 2015 ; Dieleman et al, 2014a). Finally, MR perfusion weighted imaging (PWI) may benefit from 7 T, for instance by the increased susceptibility effects and the lower amount of contrast agent required for dynamic susceptibility contrast (DSC) perfusion at 7 T. Thus, the advent of 7 T has during the past decade resulted in a wave of research exploring new developments in cerebrovascular imaging, which are now increasingly finding their way into clinical practice.…”

Correlation Between the Number of Lenticulostriate Arteries and Imaging of Cerebral Small Vessel Disease

“…Thus, in vivo imaging of LSAs could provide important insights and help us understand the pathophysiology and mechanism of SVD. Usually, digital subtraction angiography (DSA) is considered the gold standard when visualizing smaller arteries, including the perforating arteries (5, 6).…”