Yasutaka Fushimi

Aquaporin 4 correlates with apparent diffusion coefficient and hydrocephalus severity in the rat brain: a combined MRI-histological study.

Hydrocephalus features include ventricular dilatation and periventricular edema due to transependymal resorption of cerebrospinal fluid (CSF). Aquaporin 4 (AQP4), a water channel protein located at the blood-brain barrier, might facilitate the removal of this excess of water from the parenchyma into the blood. First, we hypothesized a link between AQP4 expression and the severity of hydrocephalus. We further hypothesized that movements of water through AQP4 could affect apparent diffusion coefficient (ADC) measurements. Communicating inflammatory hydrocephalus was induced in 45 rats, and at various stages, magnetic resonance imaging (MRI) was used to measure CSF volume and periventricular ADC, with immunostaining being used to determine periventricular AQP4. We found an up-regulation of periventricular AQP4 in hydrocephalic rats that was strongly correlated with both CSF volume (Pearson=0.87, p<0.00001) and periventricular ADC (Pearson=0.85, p<0.00001). AQP4 were first located on astrocyte endfeet, but later on the whole membrane of astrocytes that became hypertrophic in the most severe and chronic hydrocephalic rats. These results show that AQP4 expression follows an adaptative profile to the severity of hydrocephalus, which is probably a protective response mechanism. They also suggest that ADC, on top of informing about cell sizes and interstitial bulk water, might also indirectly reflect quantitative water channel expression.

Diffusion tensor fiber tractography for arteriovenous malformations : Quantitative analyses to evaluate the corticospinal tract and optic radiation

BACKGROUND AND PURPOSE: We hypothesized that diffusion tensor fiber tractography would be affected by intracranial arteriovenous malformation (AVM). The purpose of the present study was to evaluate the influence of intracranial AVM on corticospinal tract and optic radiation tractography. MATERIALS AND METHODS: The subject group comprised 34 patients with untreated intracranial AVM. Hemorrhage was present in 13 patients and absent in 21 patients. Perinidal fractional anisotropy (FA) and number of voxels along the reconstructed corticospinal and optic radiation tracts were measured, and left-to-right asymmetry indices (AIs) for those values were quantified. Patients were assigned to 1 of 3 groups: tracts distant from nidus, tracts close to nidus without neurologic symptoms, and tracts close to nidus associated with neurologic symptoms. One-way analysis of variance was used to compare differences in AI between groups. Hemorrhagic and nonhemorrhagic groups were assessed separately. RESULTS: In patients without hemorrhage, AI of optic radiation volume (P < .0001), AI of perinidal FA along corticospinal tract (P = .006), and optic radiation (P = .01) differed significantly between groups. In patients associated with hemorrhage, AI of corticospinal tract volume (P = .01), AI of perinidal FA along corticospinal tract (P = .04), and optic radiation (P = .004) differed significantly between groups. CONCLUSIONS: Corticospinal tract and optic radiation tractography were visualized in patients with AVM. In patients with both hemorrhagic and nonhemorrhagic AVM, the 2 fiber tracts close to the nidus were less visualized in the affected hemisphere than those distant from the nidus. Tracts were less visualized in patients with neurologic symptoms than in asymptomatic patients.

Microbleeds in moyamoya disease: susceptibility-weighted imaging versus T2*-weighted imaging at 3 Tesla.

Objectives:To prospectively evaluate differences in detectability of cerebral microbleeds (MBs) in Moyamoya disease (MMD) on susceptibility-weighted imaging (SWI) and T2*-weighted imaging (T2*WI) at 3 T. Materials and Methods:SWI and T2*WI were applied for 50 consecutive MMD patients. MB was defined as a very low signal intensity area in each sequence without continuity from surrounding vessel structures. Numbers of MBs were compared between the 2 sequences. To assess visualization, a grading score was assigned to each MB from Grade 3 (prominent) to Grade 0 (normal-appearing) on SWI and T2*WI, respectively, and were compared by Wilcoxon signed rank test. Results:A total of 37 MBs were detected in 21 patients (42%) on SWI, compared with 27 MBs in 16 patients (32%) on T2*WI, with significant difference in number of MBs between the 2 sequences (P = 0.002). Lesions displayed greater visual grading score on SWI than on T2*WI (P < 0.0001). Conclusions:SWI offers better detectability of MBs in MMD than T2*WI at 3 T.

Target bypass: a method for preoperative targeting of a recipient artery in superficial temporal artery-to-middle cerebral artery anastomoses.

OBJECTIVE: To introduce a method for preoperative targeting of a proper recipient artery in superficial temporal artery-to-middle cerebral artery anastomosis. METHODS: Six operations for superficial temporal artery-to-middle cerebral artery anastomosis in four patients with moyamoya disease or moyamoya-like disease and two operations in two patients with atherosclerotic cerebrovascular occlusive disease accompanied by coronary artery stenosis were performed using our method. Before surgery, a 3-Tesla magnetic resonance imaging study was performed with axial T1-weighted three-dimensional magnetization-prepared rapid acquisition gradient-echo sequences and three-dimensional time-of-flight magnetic resonance angiography. Data on quantitative regional cerebral blood flow were obtained by iodine-123-labeled N-isopropyl-iodoamphetamine single-photon emission computed tomography or positron emission computed tomography. The magnetic resonance angiography and regional cerebral blood flow data sets were registered with the magnetization-prepared rapid acquisition gradient-echo data set by means of the coregistration function of the SPM2 software. We examined the arteries located on or near the cortex where the regional cerebral blood flow had significantly decreased and used the coregistered data set and MRIcro software to select the cortical artery with the largest diameter as the target recipient artery. At the surgery, the data sets were applied to the neuronavigation system and the actual site of the target was confirmed in the operation before scalp incision. The superficial temporal artery was anastomosed with the target through a small craniotomy. RESULTS: Successful bypass surgery to the target was confirmed in all cases. CONCLUSION: The “target bypass” method might be effective for cases with moyamoya disease or for cases requiring surgery through a small craniotomy.

Visualization of Periventricular Collaterals in Moyamoya Disease with Flow-sensitive Black-blood Magnetic Resonance Angiography: Preliminary Experience

Fragile abnormal collaterals in moyamoya disease, known as “moyamoya vessels,” have rarely been defined. While flow-sensitive black-blood magnetic resonance angiography (FSBB-MRA) is a promising technique for visualizing perforating arteries, as of this writing no other reports exist regarding its application to moyamoya disease. Six adults with moyamoya disease underwent FSBB-MRA. It depicted abnormal collaterals as extended lenticulostriate, thalamic perforating, or choroidal arteries, which were all connected to the medullary or insular artery in the periventricular area and supplied the cortex. This preliminary case series illustrates the potential for FSBB-MRA to reveal abnormal moyamoya vessels, which could be reasonably defined as periventricular collaterals.

Quantitative Susceptibility Mapping at 3 T and 1.5 T: Evaluation of Consistency and Reproducibility.

ObjectivesThe aim of this study was to assess the consistency and reproducibility of quantitative susceptibility mapping (QSM) at 3-T and 1.5-T magnetic resonance (MR) scanners. Materials and MethodsThis study was approved by institutional ethics committee, and written informed consent was obtained. Twenty-two healthy volunteers underwent 2 examinations on different days. Each examination consisted of MR imaging on both 3-T and 1.5-T MR scanners. The data from both scanners and examination days were obtained, and QSM was calculated with STI Suite using 2 different algorithms—harmonic phase removal using laplacian operator (HARPERELLA) and a sophisticated harmonic artifact reduction for phase data (SHARP) method with a variable radius of the spherical kernel at the brain boundary (V-SHARP). We evaluated consistency of QSM between 3 T and 1.5 T and the reproducibility between the first and second examinations using 2-phase processing methods (HARPERELLA and V-SHARP). ResultsSusceptibility values of regions of interests at 3 T were highly correlated with those at 1.5 T with good agreement (HARPERELLA, R2 = 0.838; V-SHARP, R2 = 0.898) (average difference, ±1.96 SD; HARPERELLA, −0.012 ± 0.046; V-SHARP, −0.002 ± 0.034). Reproducibility analysis demonstrated excellent correlation between the first and second examination at both 3 T and 1.5 T for both algorithms (HARPERELLA at 3 T, R2 = 0.921; 1.5 T, R2 = 0.891; V-SHARP at 3 T, R2 = 0.937; 1.5 T, R2 = 0.926). Bland-Altman analysis showed excellent reproducibility for HARPERELLA (3 T, −0.003 ± 0.032; 1.5 T, −0.003 ± 0.038) and V-SHARP (3 T, −0.003 ± 0.027; 1.5 T, −0.003 ± 0.029). Susceptibility values of these 2 algorithms were highly correlated with good agreement (3T, R2 = 0.961; 1.5 T, R2 = 0.931) (3 T, 0.009 ± 0.023; 1.5 T, −0.003 ± 0.049). ConclusionsQuantitative susceptibility mapping with HARPERELLA and V-SHARP demonstrated good reproducibility at 3 T and 1.5 T, and QSM with V-SHARP demonstrated good consistency at 3 T and 1.5 T.

A Developmental Venous Anomaly Presenting Atypical Findings on Susceptibility-Weighted Imaging

Developmental venous anomaly (DVA) is the most common type of vascular malformation found at autopsy, with a prevalence of 2%.[1][1] DVA is composed of radially arranged venous complexes converging to a centrally located venous trunk, which drains the normal brain parenchyma.[2][2] Susceptibility-

Quantitative assessment of gadolinium deposition in dentate nucleus using quantitative susceptibility mapping

Gadolinium deposition in dentate nucleus (DN) has been reported after serial administration of gadolinium‐based contrast agents (GBCAs). Gadolinium complexes have paramagnetic properties; therefore, we evaluated susceptibility changes of gadolinium deposition in DN using quantitative susceptibility mapping (QSM) for patients after serial administration of GBCAs.

MR imaging of Liliequist's membrane

Liliequists membrane is an arachnoid structure well-known to neurosurgeons. However, the importance of this membrane had been lost until the development of endoscopic third ventriculostomy (ETV). ETV is superior in its minimal invasiveness, but in some subgroups of hydrocephalus, the effectiveness of ETV may be reduced. Liliequists membrane may block the cerebrospinal fluid (CSF) flow from the defect of the third ventricle floor, which may cause failure of ETV. Liliequists membrane can be visualized on magnetic resonance (MR) imaging in normal healthy individuals, however, its visibility is different among individuals. CSF artifacts exist to varying degrees, but do not impede visualization of Liliequists membrane in most subjects. Since Liliequists membrane is a cisternal structure, the three-dimensional (3D) constructive interference in steady state (CISS) sequence is useful. The outcome of ETV could be predicted with MR imaging findings of Liliequists membrane in a patient with obstructive hydrocephalus. High-field (≥3 Tesla) MR imaging of Liliequists membrane also offers superior resolution and is expected to provide additional information about Liliequists membrane.

MP2RAGE for deep gray matter measurement of the brain: A comparative study with MPRAGE

To compare magnetization‐prepared two rapid acquisition gradient echoes (MP2RAGE) imaging with conventional MPRAGE imaging for deep gray matter (GM) segmentation, reproducibility, contrast ratio (CR) and contrast‐to‐noise ratio (CNR), and to evaluate reproducibility of T1 maps derived from MP2RAGE.