Intracranial Vessel Wall MR Imaging: From Bench to Bedside

Intracranial vessel wall MR Imaging is an emerging MRI-technique that has gained an increasing popularity in the last decade because of its potential applications in a variety of intracranial vascular diseases. However, intracranial vessel wall MRI has not been systematically applied in clinical setting yet. In this thesis, the clinical translation has been made from research to clinical practice. First, we describe how intracranial vessel wall MRI should be used and how the images should be interpreted. Second, we show with clinical-epidemiological studies the additional value of this MRI-technique. We show that vessel wall lesions, detected with intracranial vessel wall MRI, are associated with several cardiovascular risk factors and with damage of the brain parenchyma itself. Furthermore, we assess with ultra-high resolution (7 tesla) MRI possible vessel wall damage after intra-arterial thrombectomy (IAT). The results suggest reactive changes of the vessel wall after IAT which should be taken into consideration during follow-up MRI of the vessel wall. Ultimately, we think that intracranial vessel wall MRI has the strong potential to be implemented in the workup and follow-up of patients with cerebrovascular disease, in risk management, and in diagnosing other vasculopathies, using it as non-invasive diagnostic tool to guide preventive and therapeutic decision-making

Spinal Dural Arterio-venous Fistulas : The Utility and Accuracy of Contrast-Enhanced MR Angiography for Localization of Spinal Dural Arteriovenous Fistulas

Background and purpose: Spinal Dural Arteriovenous Fistulas (SDAVFs) are challenging to diagnose. Often the diagnosis is made when advanced neurological symptoms are present. Radiological examination plays a key role in making the diagnosis. Conventional MR imaging may give raise to the suspicion of a SDAVF and contrast-enhanced MR angiography (CE-MRA) can serve as a useful non-invasive examination to detect SDAVFs and predict their location prior to digital subtraction angiography (DSA). Few experiences are published with CE-MRA but only in preliminary fashion or comprised small number of cases. By using CE-MRA as guidance for selective DSA, burdensome DSA can be avoided. The purpose of this study was to determine the utility and accuracy of contrast-enhanced MR angiography in Spinal Dural Arteriovenous Fistulas in a large number of cases. Methods: A retrospective analysis from 1999 – 2012 in the Toronto Western Hospital/University Health Network (TWH/UHN) identified 70 patients clinically suspected of harboring a SDAVF. Each patient underwent conventional MR imaging, CE-MRA and DSA. We evaluated for the presence or absence of serpentine flow voids, T2-weighted hyperintensity and patchy cord enhancement on conventional MR imaging as well as the level and side of the fistula as predicted by CE-MRA. DSA was used as the reference standard for the true location of the fistula. Institutional Research Ethic Board approval was obtained. Results: Of the 70 cases, 53 were determined to be a SDAVF, 10 cases were shown to be other forms of spinal vascular malformation and 7 were negative on DSA. On conventional MR imaging all reported cases of SDAVF showed serpentine flow voids (100%). T2-weighted hyperintensity was seen in 96% extending to the conus in 85% of cases. Patchy cord enhancement was seen in 93%. CE-MRA correctly localized the level and side of the SDAVF in 43 of the 53 cases (81%). Conclusion: CE-MRA is a useful non-invasive examination in the detection of the level and side of a SDAVF. A negative CE-MRA combined with negative conventional MR imaging can exclude a SDAVF and obviate the need for DSA. CE-MRA facilitates but does not replace diagnostic DSA in cases of SDAVF as confirmation of specific location, type of fistula and arterial detail are required prior to contemplated treatment of these lesions.

The Use and Pitfalls of Intracranial Vessel Wall Imaging : How We Do It

Intracranial vessel wall magnetic resonance (MR) imaging has gained much attention in the past decade and has become part of state-of-the-art MR imaging protocols to assist in diagnosing the cause of ischemic stroke. With intracranial vessel wall imaging, vessel wall characteristics have tentatively been described for atherosclerosis, vasculitis, dissections, Moyamoya disease, and aneurysms. With the increasing demand and subsequently increased use of intracranial vessel wall imaging in clinical practice, radiologists should be aware of the choices in imaging parameters and how they affect image quality, the clinical indications, methods of assessment, and limitations in the interpretation of these images. In this How I do It article, the authors will discuss the technical requirements and considerations for vessel wall image acquisition in general, describe their own vessel wall imaging protocol at 3 T and 7 T, show a step-by-step basic assessment of intracranial vessel wall imaging as performed at their institution-including commonly encountered artifacts and pitfalls-and summarize the commonly reported imaging characteristics of various intracranial vessel wall diseases for direct clinical applicability. Finally, future technical and clinical considerations for full implementation of intracranial vessel wall imaging in clinical practice, including the need for histologic validation and acquisition time reduction, will be discussed

The accuracy and utility of contrast-enhanced MR angiography for localization of spinal dural arteriovenous fistulas: the Toronto experience

The purpose of this study was to determine the accuracy and utility of contrast-enhanced MR angiography (CE-MRA) in spinal dural arteriovenous fistulas (SDAVF). A retrospective analysis from 1999-2012 identified 70 patients clinically suspected of harboring a SDAVF. Each patient underwent consecutive conventional MR-imaging, CE-MRA, and digital subtraction angiography (DSA). The presence or absence of serpentine flow voids, T2-weighted hyperintensity, and cord enhancement were evaluated, as well as location of the fistula as predicted by CE-MRA. DSA was used as the reference standard. Of the 70 cases, 53 were determined to be a SDAVF, 10 cases were shown to be other forms of vascular malformation, and 7 were DSA-negative. On MRI, all reported cases of SDAVF showed serpentine flow voids (100 %). T2-weighted hyperintensity was seen in 48 of 50 cases (96 %), extending to the conus in 41 of 48 cases (85 %). Cord enhancement was seen in 38 of 41 cases (93 %). CE-MRA correctly localized the SDAVF in 43 of the 53 cases (81 %). CE-MRA is a useful non-invasive examination for the detection and localization of SDAVF. CE-MRA facilitates but does not replace DSA as confirmation of location, fistula type, and arterial detail, which are required before treatment. aEuro cent CE-MRA correctly localized the site of the SDAVF in over 80 % of cases. aEuro cent CE-MRA facilitates diagnostic DSA and expedites the diagnostic process. aEuro cent CE-MRA does not replace diagnostic DSA in SDAVF cases as confirmative test. aEuro cent CE-MRA provides better understanding of missed or mislocalized SDAVF cases

Clinical Vascular Imaging in the Brain at 7 T

Stroke and related cerebrovascular diseases are a major cause of mortality and disability. Even at standard-field-strengths (1.5T), MRI is by far the most sensitive imaging technique to detect acute brain infarctions and to characterize incidental cerebrovascular lesions, such as white matter hyperintensities, lacunes and microbleeds. Arterial time-of-flight (TOF) MR angiography (MRA) can depict luminal narrowing or occlusion of the major brain feeding arteries, and this without the need for contrast administration. Compared to 1.5T MRA, the use of high-field strength (3T) and even more so ultra-high-field strengths (7T), enables the visualization of the lumen of much smaller intracranial vessels, while adding a contrast agent to TOF MRA at 7T may enable the visualization of even more distal arteries in addition to veins and venules. Moreover, with 3T and 7T, the arterial vessel walls beyond the circle of Willis become visible with high-resolution vessel wall imaging. Also, with 7T MRI, the brain parenchyma can now be visualized on a submillimeter scale. As a result, high-resolution imaging studies of the brain and its blood supply at 7T have generated new concepts of different cerebrovascular diseases. In the current article, we will discuss emerging clinical applications and future directions of vascular imaging in the brain at 7T MRI

Contrast leakage distant from the hematoma in patients with spontaneous ICH: A 7 T MRI study

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Contrast leakage distant from the hematoma in patients with spontaneous ICH : A 7 T MRI study

Disruption of the blood-brain barrier (BBB) might play a role in the pathophysiology of cerebral small vessel disease-related ICH. The aim of this study was to assess presence and extent of contrast agent leakage distant from the hematoma as a marker of BBB disruption in patients with spontaneous ICH. We prospectively performed 7 tesla MRI in adult patients with spontaneous ICH and assessed contrast leakage distant from the hematoma on 3D FLAIR images. Thirty-one patients were included (mean age 60 years, 29% women). Median time between ICH and MRI was 20 days (IQR 9-67 days). Seventeen patients (54%; seven lobar, nine deep, one infratentorial ICH) had contrast leakage, located cortical in 16 and cortical and deep in one patient. Patients with contrast leakage more often had lobar cerebral microbleeds (CMBs; 77%) than those without (36%; RR 2.5, 95% CI 1.1-5.7) and a higher number of lobar CMBs (patients with contrast leakage: median 2, IQR 1-8 versus those without: median 0, IQR 0-2; p = 0.02). This study shows that contrast leakage distant from the hematoma is common in days to weeks after spontaneous ICH. It is located predominantly cortical and related to lobar CMBs and therefore possibly to cerebral amyloid angiopathy