Vessel Wall Characterization Using Quantitative MR Imaging.

MR imaging's exceptional capabilities in vascular imaging stem from its ability to visualize and quantify vessel wall features, such as plaque burden, composition, and biomechanical properties. The application of advanced MR imaging techniques, including two-dimensional and three-dimensional black-blood MR imaging, T1 and T2 relaxometry, diffusion-weighted imaging, and dynamic contrast-enhanced MR imaging, wall shear stress, and arterial stiffness, empowers clinicians and researchers to explore the intricacies of vascular diseases. This array of techniques provides comprehensive insights into the development and progression of vascular pathologies, facilitating earlier diagnosis, targeted treatment, and improved patient outcomes in the management of vascular health.

Detection of Angiographically Occult Ruptured Basilar Sidewall Perforator Aneurysm by Vessel Wall MR Imaging.

Basilar artery perforator aneurysms are rare with a prevalence of less than 1%. These are particularly challenging to detect given their small size and tendency to intermittently thrombose. We describe a case of a ruptured basilar artery sidewall perforator aneurysm that was angiographically occult on computed tomographic angiogram and cerebral catheter angiogram. One day after the initial diagnostic work-up, intracranial vessel wall MR imaging (VWI) was performed which revealed a small outpouching along the right posterolateral basilar arterial wall with a punctate enhancing focus suggestive of a thrombosed basilar perforator artery aneurysm. Thrombus within the small aneurysm sac likely contributed to the poor opacification of the aneurysm sac on conventional lumen-based imaging techniques. Ruptured aneurysms have high morbidity and mortality due to their tendency to rebleed, making their expedient detection and treatment imperative. This case highlights the role VWI can play in detecting small ruptured aneurysms that intermittently thrombose and are otherwise challenging to diagnose with conventional vessel imaging.

High-Resolution Neurovascular Imaging at 7T: Arterial Spin Labeling Perfusion, 4-Dimensional MR Angiography, and Black Blood MR Imaging.

Ultrahigh field offers increased resolution and contrast for neurovascular imaging. Arterial spin labeling methods benefit from an increased intrinsic signal-to-noise ratio of MR imaging signal and a prolonged tracer half-life at ultrahigh field, allowing the visualization of layer-dependent microvascular perfusion. Arterial spin labeling-based time-resolved 4-dimensional MR angiography at 7T provides a detailed depiction of the vascular architecture and dynamic blood flow pattern with high spatial and temporal resolutions. High-resolution black blood MR imaging at 7T allows detailed characterization of small perforating arteries such as lenticulostriate arteries. All techniques benefit from advances in parallel radiofrequency transmission technologies at ultrahigh field.

Vessel wall MR imaging of intracranial atherosclerosis.

Intracranial atherosclerotic disease (ICAD) is one of the most common causes of ischemic stroke worldwide. Along with high recurrent stroke risk from ICAD, its association with cognitive decline and dementia leads to a substantial decrease in quality of life and a high economic burden. Atherosclerotic lesions can range from slight wall thickening with plaques that are angiographically occult to severely stenotic lesions. Recent advances in intracranial high resolution vessel wall MR (VW-MR) imaging have enabled imaging beyond the lumen to characterize the vessel wall and its pathology. This technique has opened new avenues of research for identifying vulnerable plaque in the setting of acute ischemic stroke as well as assessing ICAD burden and its associations with its sequela, such as dementia. We now understand more about the intracranial arterial wall, its ability to remodel with disease and how we can use VW-MR to identify angiographically occult lesions and assess medical treatment responses, for example, to statin therapy. Our growing understanding of ICAD with intracranial VW-MR imaging can profoundly impact diagnosis, therapy, and prognosis for ischemic stroke with the possibility of lesion-based risk models to tailor and personalize treatment. In this review, we discuss the advantages of intracranial VW-MR imaging for ICAD, the potential of bioimaging markers to identify vulnerable intracranial plaque, and future directions of artificial intelligence and its utility for lesion scoring and assessment.

Quantitative comparisons between relaxation enhanced compressed sensing 3D MERGE and conventional 3D MERGE for vessel wall imaging in equal scan time: preliminary studies.

In this study, we quantitatively compared relaxation enhanced compressed sensing (RECS-3D MERGE) with conventional 3D MERGE techniques on blood suppression efficiency, wall-lumen contrast and plaque burden measurement for carotid atherosclerotic imaging in equal scan time. Twelve patients were recruited in the study. RECS-3D MERGE and conventional 3D MERGE were implemented. 2D DIR-FSE was carried out as a reference standard. The lumen signal-to-tissue ratio (STR) was used as the quantitative measure of blood suppression efficiency. The contrast-to-tissue ratio (CTR) was used as the quantitative measure of wall-lumen contrast. Vessel lumen area (LA) and wall area (WA) were measured for morphological comparisons. The lumen STR of RECS-3D MERGE was significantly lower than that of 3D MERGE while the wall-lumen CTR of RECS-3D MERGE was significantly higher. There were no significant differences in plaque burden measurements between RECS-3D MERGE and 2D DIR-FSE. For comparison between conventional 3D MERGE and 2D DIR-FSE, there were no significant differences in LA measurement. However, the WA of 3D MERGE was significantly larger. The RECS-3D MERGE sequence achieved more sufficient blood suppression and higher image contrast without prolonging the scan time. These improvements lead to more accurate morphological measurements of carotid atherosclerotic imaging.