Wall Contrast Enhancement of Thrombosed Intracranial Aneurysms at 7T MRI.

BACKGROUND AND PURPOSE: The pathophysiology of wall contrast enhancement in thrombosed intracranial aneurysms is incompletely understood. This in vivo study aimed to investigate wall microstructures with gadolinium-enhanced 7T MR imaging. MATERIALS AND METHODS: Thirteen patients with 14 thrombosed intracranial aneurysms were evaluated using a 7T whole-body MR imaging system with nonenhanced and gadolinium-enhanced high-resolution MPRAGE. Tissue samples were available in 5 cases, and histopathologic findings were correlated with 7T MR imaging to identify the gadolinium-enhancing microstructures. RESULTS: Partial or complete inner wall enhancement correlated with neovascularization of the inner wall layer and the adjacent thrombus. Additional partial or complete outer wall enhancement can be explained by formation of vasa vasorum in the outer aneurysm wall layer. The double-rim enhancement correlated with perifocal edema and wall histologic findings suggestive of instability. CONCLUSIONS: Two distinct aneurysm wall microstructures responsible for gadolinium enhancement not depictable at lower spatial resolutions can be visualized in vivo using high-resolution gadolinium-enhanced 7T MR imaging.

Detection of in-stent protrusion (ISP) by intravascular ultrasound during carotid stenting: Usefulness of stent-in-stent placement for ISP.

OBJECTIVES: As in-stent protrusion (ISP) during carotid artery stenting (CAS) may cause postoperative embolism, ISP detection is important. Intravascular ultrasound examination (IVUS) is useful for ISP detection because the blood vessel cross-section can be drawn as a tomogram from the lumen. Our objective was to clarify the occurrence of ISP during CAS using IVUS and relevant factors, and to report the usefulness of stent-in-stent placement when treating ISP. METHODS: In 142 consecutive patients (128 men, average age 71.7 years; 69 symptomatic) who underwent CAS using dual protection and the blood aspiration method, and subsequent IVUS after stent placement were included. The outcome of CAS, and the occurrence rate of ISP and related factors (plaque characteristics, stent design, intraoperative debris capture rate and postoperative diffusion-weighted imaging (DWI) positive rate) were examined. RESULTS: All CAS procedures were successful and no major adverse events (MAEs) were observed at 30 days. ISP was found in 12% (17/142), and stent-in-stent placement was performed in all cases. Vulnerable plaques were observed in 12 of 17 ISP cases (71%). A closed stent was used in 13 of 17 ISP cases (71%). The intraoperative debris capture rate was 100%, and no neurological symptoms were observed in any patients. A significant increase in ISP susceptibility was related to vulnerable plaques and the intraoperative debris capture rate. CONCLUSIONS: Vulnerable plaques and debris capture were significantly correlated with ISP occurrence. In all ISP cases, stent-in-stent placement was performed and good results were obtained. KEY POINTS: • ISP detection during CAS using IVUS is important. • ISP-positive patients were correlated with NASCET ≥ 80%, vulnerable plaques and stent length. • Adequate additional treatment of stent in stenting under reliable protection against ISP-positive patients achieved low perioperative complications.

Visualization and Classification of Deeply Seated Collateral Networks in Moyamoya Angiopathy with 7T MRI.

BACKGROUND AND PURPOSE: Collateral networks in Moyamoya angiopathy have a complex angioarchitecture difficult to comprehend on conventional examinations. This study aimed to evaluate morphologic patterns and the delineation of deeply seated collateral networks using ultra-high-field MRA in comparison with conventional DSA. MATERIALS AND METHODS: Fifteen white patients with Moyamoya angiopathy were investigated in this prospective trial. Sequences acquired at 7T were TOF-MRA with 0.22 × 0.22 × 0.41 mm3 resolution and MPRAGE with 0.7 × 0.7 × 0.7 mm3 resolution. Four raters evaluated the presence of deeply seated collateral networks and image quality in a consensus reading of DSA, TOF-MRA, and MPRAGE using a 5-point scale in axial source images and maximum intensity projections. Delineation of deeply seated collateral networks by different imaging modalities was compared by means of the McNemar test, whereas image quality was compared using the Wilcoxon signed-rank test. RESULTS: The relevant deeply seated collateral networks were classified into 2 categories and 6 pathways. A total of 100 collateral networks were detected on DSA; 106, on TOF-MRA; and 73, on MPRAGE. Delineation of deeply seated collateral networks was comparable between TOF-MRA and DSA (P = .25); however, both were better than MPRAGE (P < .001). CONCLUSIONS: This study demonstrates excellent delineation of 6 distinct deeply seated collateral network pathways in Moyamoya angiopathy in white adults using 7T TOF-MRA, comparable to DSA.

Ventricular Microaneurysms in Moyamoya Angiopathy Visualized with 7T MR Angiography.

The pathophysiologic role of hemodynamic alteration to peripheral vessels in Moyamoya angiopathy and the formation of microaneurysms remains unclear. The purpose of this study was to investigate microaneurysms in collateral Moyamoya vessels by using 7T ultra-high-field MR imaging. Ten patients with Moyamoya disease were evaluated with TOF-MRA at 7T acquired with 0.22 × 0.22 × 0.41 mm(3) resolution. In 10 patients, 4 microaneuryms located in the ventricles were delineated. The mean diameters of collateral vessels and microaneurysms arising from those vessels were 0.87 mm (range, 0.79-1.07 mm) and 0.80 mm (range, 0.56-0.96 mm), respectively. In 1 case with follow-up scans 6 months after a direct extracranial-intracranial bypass operation, the microaneurysm disappeared. Ventricular microaneurysms in Moyamoya angiopathy collateral vessels, inaccessible by conventional imaging techniques, can be detected by 7T TOF-MRA.

Giant Intracranial Aneurysms at 7T MRI.

Giant intracranial aneurysms are rare vascular pathologies associated with high morbidity and mortality. The purpose of this in vivo study was to assess giant intracranial aneurysms and their wall microstructure by 7T MR imaging, previously only visualized in histopathologic examinations. Seven giant intracranial aneurysms were evaluated, and 2 aneurysms were available for histopathologic examination. Six of 7 (85.7%) showed intraluminal thrombus of various sizes. Aneurysm walls were depicted as hypointense in TOF-MRA and SWI sequences with excellent contrast ratios to adjacent brain parenchyma (range, 0.01-0.60 and 0.58-0.96, respectively). The triple-layered microstructure of the aneurysm walls was visualized in all aneurysms in TOF-MRA and SWI. This could be related to iron deposition in the wall, similar to the findings in 2 available histopathologic specimens. In vivo 7T TOF-MRA and SWI can delineate the aneurysm wall and the triple-layered wall microstructure in giant intracranial aneurysms.

Vascular Wall Imaging of Unruptured Cerebral Aneurysms with a Hybrid of Opposite-Contrast MR Angiography.

BACKGROUND AND PURPOSE: Inflammation and degeneration of the intracranial saccular aneurysm wall play a major role in aneurysm formation, development and subsequent rupture. The aim of this study was to characterize the walls of unruptured intracranial aneurysms by using a hybrid of opposite-contrast MRA at 3T. MATERIALS AND METHODS: Fourteen consecutive patients with 17 unruptured intracranial aneurysms who initially underwent clipping surgery were prospectively evaluated. All aneurysms were scanned preoperatively by using a hybrid of opposite-contrast MRA in 3T high-resolution MR imaging. We classified intraoperative findings of atherosclerotic plaques in the aneurysms into 3 grades: grade A (major plaques), grade B (minor plaques), and grade C (no plaques). The contrast ratio of the high-intensity area was also measured relative to the background low-intensity area inside the carotid artery. RESULTS: Findings from preoperative plaque imaging of the aneurysm corresponded to the intraoperative findings in 15 of 16 aneurysms (excluding 1 that was impossible to visualize in its entirety due to anatomic reasons). Overall sensitivity and specificity of the hybrid of opposite-contrast MRA were 88.9% and 100%, respectively. During the operation, 4 aneurysms were classified as grade A; 5, as grade B; and 7, as grade C. The means of the contrast ratio for grades A, B, and C were 0.72 ± 0.03, 0.34 ± 0.30, and -0.02 ± 0.09, respectively. CONCLUSIONS: The hybrid of opposite-contrast MRA can detect visible atherosclerotic plaques in the unruptured aneurysm wall, and the contrast ratio in intracranial aneurysms correlated with their presence and extent. A study including a larger series is needed to validate the diagnostic potential of this imaging technique.

[A case of juvenile pilocytic astrocytoma with unusual neuroimaging features].

We present a case of cerebellar juvenile pilocytic astrocytoma(JPA) with unusual neuroimaging features. The patient was a 14-year-old male who suffered from chronic headaches for a couple of weeks. Plain craniogram showed a decalcification and bulging of the occipital bone. Computed tomography(CT) scans demonstrated low density multiple components with small calcifications in the right cerebellar hemisphere extending to the left. These calcifications were found at the margin of these multi-lobular components. Magnetic resonance imaging(MRI) revealed iso or low intensity on T1 weighted image, and slightly high intensity on T2 weighted image. The lesion indicated more heterogeneous and higher intensity than brain parenchyma on FLAIR imaging, and remarkable higher intensity than brain parenchyma with some small low intensity areas on diffusion weighted imaging. He underwent the complete resection except for the cranial tissue surrounding the pons. Histologic diagnosis was juvenile pilocytic astrocytoma, because of biphasic pattern of bipolar cells and a number of Rosenthal fibers. Generally JPA has sharp and smooth demarcated cysts with well-enhanced mural nodule. It was difficult to diagnose the presented tumor as JPA before operation, since its unusual neuroimaging resembled both dermoid and high grade gliomas.

[A case of convexity meningioma en plaque].

We present a case of convexity meningioma en plaque (MEP). A 51-year-old male occasionally suffering from right parietalgia and numbness of left upper limb. An intracranial abnormal mass was pointed out incidentally by the brain check up. Computed tomographic (CT) scans demonstrated a hyperostosis and an enhanced abnormal mass at the right front-parietal region. Magnetic resonant images (MRI) revealed a carpet like tumor extended along the dura mater. Cerebral angiography disclosed feedings from parietal branches of right middle meningeal artery and superficial temporal artery. The tumor was removed subtotally with adjacent dura mater, leaving the portion of close adhesion to the brain parenchyma. Histologic diagnosis was transitional meningioma. Immunohistological stainings showed a high staining index (6.9%) of MIB-1 (Ki-69 antigen) and high expression of metalloproteinase-9 (MMP-9), especially along the dura mater. Convexity MEP is so rare that we review previous reported cases of convexity MEP, and discuss the clinicopathologic features on that.