Contemporary and emerging magnetic resonance imaging methods for evaluation of moyamoya disease

Abstract

<jats:p>Numerous recent technological advances offer the potential to substantially enhance the MRI evaluation of moyamoya disease (MMD). These include high-resolution volumetric imaging, high-resolution vessel wall characterization, improved cerebral angiographic and perfusion techniques, high-field imaging, fast scanning methods, and artificial intelligence. This review discusses the current state-of-the-art MRI applications in these realms, emphasizing key imaging findings, clinical utility, and areas that will benefit from further investigation. Although these techniques may apply to imaging of a wide array of neurovascular or other neurological conditions, consideration of their application to MMD is useful given the comprehensive multidimensional MRI assessment used to evaluate MMD. These MRI techniques span from basic cross-sectional to advanced functional sequences, both qualitative and quantitative.</jats:p><jats:p>The aim of this review was to provide a comprehensive summary and analysis of current key relevant literature of advanced MRI techniques for the evaluation of MMD with image-rich case examples. These imaging methods can aid clinical characterization, help direct treatment, assist in the evaluation of treatment response, and potentially improve the understanding of the pathophysiology of MMD.</jats:p>

Implementation and Rationale for a Unified Clinical and Imaging Protocol for Evaluation and Treatment of Moyamoya Angiopathy: A Single Institutional Experience

“…Evaluation of these patterns, in addition to determining the diameter and contribution to the intracranial blood supply by various external carotid artery branches enables for planning of potential surgical intervention in cases where it may be indicated. Indeed, DSA is largely considered as the gold standard for evaluation of MMD given its high spatial and temporal resolution (19). Additionally, CT examinations, including CTA and computed tomography perfusion (CTP) may be used in select circumstances such as detailed evaluation of a direct bypass (Figure 2) or emergency evaluations (Figure 3).…”

“…High-resolution vessel wall imaging (HR-VWI) consists of a variety of MRI techniques that provide sub-millimeter resolution and suppression of surrounding signal from flowing blood which enables assessment of the arterial wall (20). The most consistent feature of MMD on HR-VWI is negative remodeling of the involved segments (decreased outer wall diameter), although vessel wall enhancement and thickening are also reported (19,21,22). The primary utility of HR-VWI lies in diagnosing and distinguishing idiopathic MMD from other disease processes which may appear similar on conventional luminal imaging modalities, such as intracranial atherosclerosis (23).…”

“…Standard cross-sectional MRI images allow assessment of numerous important findings including the "ivy sign, " white matter T2 hyperintensity burden, ischemic or hemorrhage infarct, volume loss amongst other findings (19). The precise pulse sequences used will rely on availability and local practice patterns.…”

“…Volumetric (rather than 2D) T2 fluid-attenuated inversion recovery (FLAIR) images facilitate fusion with blood-oxygen level dependent cerebrovascular reactivity (BOLD CVR) maps and potential for white matter T2 hyperintensity quantification. An echo-planar gradient echo sequence is used instead of a susceptibility-weighted imaging sequence due to time considerations, although some features of MMD may be more conspicuous on the latter (19). Of course, standard diffusionweighted images (DWI) are obtained in addition to the aforementioned.…”

The Effect of Extracranial‐to‐Intracranial Bypass on Cerebral Vasoreactivity: A 4D Flow MRI Pilot Study

“…While noninvasive imaging techniques such as computed tomography angiography (CTA) and time of flight MR angiography (TOF‐MRA) can suggest graft patency, CTA is dependent on bolus timing, and TOF‐MRA is prone to artifact and signal loss, which can lead to an overestimation of stenosis, particularly in small caliber vessels. In addition, neither CTA nor TOF‐MRA provides quantitative data regarding blood flow 9 …”