BACKGROUND AND PURPOSE:Arteriovenous malformations are an important etiology of hemorrhagic stroke. However, current imaging modalities and risk do not provide insights into individual AVM hemodynamics and its role in pathophysiology. The aims of this study are to determine whether intracranial 4D flow MR imaging can provide insights into arteriovenous malformation hemodynamics independent of the Spetzler-Martin grade and to report the changes in flow observed during staged embolization.

Purpose To employ 4D-flow MRI for the comprehensive in-vivo analysis of hemodynamics and its relationship to size and morphology of different intracranial aneurysms (IA). We hypothesize that different IA groups, defined by size and morphology, exhibit different velocity fields, wall shear stress and vorticity. Materials and Methods 4D-flow MRI (spatial resolution=0.99–1.8×0.78–1.46×1.2–1.4mm3, temporal resolution=44–48ms) was performed in 19 IAs (18 patients, age=55.4 ± 13.8 years) with saccular (n=16) and fusiform (n=3) morphology and different sizes ranging from small (n=8, largest dimension=6.2 ± 0.4mm) to large and giant (n=11, 25 ± 7mm). Analysis included quantification of volumetric spatial-temporal velocity distribution, vorticity, and wall shear stress (WSS) along the aneurysms 3D surface. Results 4D-flow MRI revealed distinct hemodynamic patterns for large/giant saccular aneurysms (Group 1), small saccular aneurysms (Group 2) and large/giant fusiform aneurysms (Group 3). Saccular IA (Groups 1, 2) demonstrated significantly higher peak velocities (p<0.002) and WSS (p<0.001) compared to fusiform aneurysms. Although intra-aneurysmal 3D velocity distributions were similar for Group 1 and 2, vorticity and WSS was significantly (p<0.001) different (increased in Group 1 by 54%) indicating a relationship between IA size and hemodynamics. Group 3 showed reduced velocities (p<0.001) and WSS (p<0.001). Conclusion 4D flow MRI demonstrated the influence of lesion size and morphology on aneurysm hemodynamics suggesting the potential of 4D-flow MRI to assist in the classification of individual aneurysms.

Background & Aims-We have previously utilized a novel biomedical optics technology, fourdimensional elastically-scattered light fingerprinting, to demonstrate that in experimental colon carcinogenesis, the predysplastic epithelial microvascular blood content is markedly elevated. In order to assess the potential clinical translatability of this putative field effect marker, we characterized the early increase in blood supply (EIBS) in humans in vivo.

In this pilot study, we determined that intraplaque enhancement could be reliably evaluated with the use of cross-sectional imaging and analysis of vessels/plaques by use of conventional neuroanatomic MR imaging protocols. In addition, we observed a strong association between intraplaque enhancement in severe intracranial atherosclerotic disease lesions and ischemic events with the use of conventional MR imaging. Our preliminary study suggests that T1 gadolinium-enhancing plaques may be an indicator of progressing or symptomatic intracranial atherosclerotic disease.

Purpose This study evaluated the feasibility of using 4D flow MRI and a semi‐automated analysis tool to assess the hemodynamic impact of intracranial atherosclerotic disease (ICAD). The ICAD impact was investigated by evaluating pressure drop (PD) at the atherosclerotic stenosis and changes in cerebral blood flow distribution in patients compared to healthy controls. Methods Dual‐venc 4D flow MRI was acquired in 25 healthy volunteers and 16 ICAD patients (ICA, N = 3; MCA, N = 13) with mild (<50%), moderate (50–69%), or severe (>70%) intracranial stenosis. A semi‐automated analysis tool was developed to quantify velocity and flow from 4D flow MRI and to evaluate cerebral blood flow redistribution. PD at stenosis was estimated using the Bernoulli equation. The PD calculation was examined by an in vitro phantom study against flow simulations. Results Flow analysis in controls indicated symmetry in blood flow rate (FR) and peak velocity (PV) between the brain hemispheres. For patients, PV in the affected hemisphere was significantly (65%) higher than the normal side (P = 0.002). However, FR to both hemispheres of the brain was the same. The PD depicted significant correlation with PV asymmetry in patients (ρ = 0.67 and P = 0.02), and it was significantly higher for severe compared to moderate stenosis (3.73 vs. 2.30 mm Hg, P = 0.02). Conclusion 4D flow MRI quantification enables assessment of the hemodynamic impact of ICAD. The significant difference of the PD between patients with severe and moderate stenosis and its correlation with PV asymmetry suggest that PD may be a pertinent hemodynamic biomarker to evaluate ICAD.

Background and Purpose This work sought to mathematically model infarct growth and determine if infarct volume growth can be predicted by angiographic assessment of pial collateral recruitment in an experimental Middle Cerebral Artery Occlusion (MCAO) animal model. Materials and Methods Pial collateral recruitment was quantified using DSA, acquired 15 minutes following permanent MCAO in six canines based on a scoring system (Pc) and arterial arrival time (AAT). MRI based infarct volumes were measured 1,1.5,2,3,4 and 24 hours following MCAO and parameterized in terms of growth rate index (G) and final infarct volume (VFinal) as V(t) = VFinal (1−e (−G*t)). Correlations of G and VFinal to Pc and AAT were assessed by linear bivariate analysis. Correlations were used to generate asymptotic models of infarct growth for Pc or AAT values. Pc and AAT based models were assessed by F-test and residual errors. Results Evaluation of pial collateral recruitment at 15 minutes post occlusion were strongly correlated with 24-hour infarct volumes (Pc: r2=0.96, p<0.003; AAT: r2=0.86, p<0.008). Infarct growth, G, had strong and moderate linear relationships to Pc (r2 = 0.89; p<0.0033) and AAT (r2 = 0.69; p<0.0419), respectively. VFinal and G were algebraically replaced by angiographically based collateral assessments to model infarct growth. F-test, demonstrated no statistical advantage to using Pc- over AAT-based predictive models despite lower residual error in the Pc-based mode (p<0.03). Conclusion In an experimental permanent MCAO model, assessment of pial collaterals correlates with infarct growth rate index and has the potential to predict asymptotic infarct volume growth.

BACKGROUND AND PURPOSE:The role of intracranial hemodynamics in the pathophysiology and risk stratification of brain AVMs remains poorly understood. The purpose of this study was to assess the influence of Spetzler-Martin grade, clinical history, and risk factors on vascular flow and tissue perfusion in cerebral AVMs.

BACKGROUND AND PURPOSE:Pathological changes in the intracranial aneurysm wall may lead to increases in its permeability; however the clinical significance of such changes has not been explored. The purpose of this pilot study was to quantify intracranial aneurysm wall permeability (K