Analysis of Cerebral Aneurysm Wall Tension and Enhancement Using Finite Element Analysis and High-Resolution Vessel Wall Imaging

Biomechanical computational simulation of intracranial aneurysms has become a promising method for predicting features of instability leading to aneurysm growth and rupture. Hemodynamic analysis of aneurysm behavior has helped investigate the complex relationship between features of aneurysm shape, morphology, flow patterns, and the proliferation or degradation of the aneurysm wall. Finite element analysis paired with high-resolution vessel wall imaging can provide more insight into how exactly aneurysm morphology relates to wall behavior, and whether wall enhancement can describe this phenomenon. In a retrospective analysis of 23 unruptured aneurysms, finite element analysis was conducted using an isotropic, homogenous third order polynomial material model. Aneurysm wall enhancement was quantified on 2D multiplanar views, with 14 aneurysms classified as enhancing (CRstalk≥0.6) and nine classified as non-enhancing. Enhancing aneurysms had a significantly higher 95th percentile wall tension (μ = 0.77 N/cm) compared to non-enhancing aneurysms (μ = 0.42 N/cm, p < 0.001). Wall enhancement remained a significant predictor of wall tension while accounting for the effects of aneurysm size (p = 0.046). In a qualitative comparison, low wall tension areas concentrated around aneurysm blebs. Aneurysms with irregular morphologies may show increased areas of low wall tension. The biological implications of finite element analysis in intracranial aneurysms are still unclear but may provide further insights into the complex process of bleb formation and aneurysm rupture.

High-resolution magnetic resonance vessel wall imaging–guided endovascular recanalization for nonacute intracranial artery occlusion

OBJECTIVE On the basis of the characteristics of occluded segments on high-resolution magnetic resonance vessel wall imaging (MR-VWI), the authors evaluated the role of high-resolution MR-VWI–guided endovascular recanalization for patients with symptomatic nonacute intracranial artery occlusion (ICAO). METHODS Consecutive patients with symptomatic nonacute ICAO that was refractory to aggressive medical treatment were prospectively enrolled and underwent endovascular recanalization. High-resolution MR-VWI was performed before the recanalization intervention. The characteristics of the occluded segments on MR-VWI, including signal intensity, occlusion morphology, occlusion angle, and occlusion length, were evaluated. Technical success was defined as arterial recanalization with modified Thrombolysis in Cerebral Infarction grade 2b or 3 and residual stenosis < 50%. Perioperative complications were recorded. The characteristics of the occluded segments on MR-VWI were compared between the recanalized group and the failure group. RESULTS Twenty-five patients with symptomatic nonacute ICAO that was refractory to aggressive medical treatment were consecutively enrolled from April 2020 to February 2021. Technical success was achieved in 19 patients (76.0%). One patient (4.0%) had a nondisabling ischemic stroke during the perioperative period. Multivariable logistic analysis showed that successful recanalization of nonacute ICAO was associated with occlusion with residual lumen (OR 0.057, 95% CI 0.004–0.735, p = 0.028) and shorter occlusion length (OR 0.853, 95% CI 0.737–0.989, p = 0.035). CONCLUSIONS The high-resolution MR-VWI modality could be used to guide endovascular recanalization for nonacute ICAO. Occlusion with residual lumen and shorter occlusion length on high-resolution MR-VWI were identified as predictors of technical success of endovascular recanalization for nonacute ICAO.

P.115 Vessel Wall Imaging of Unusual Childhood Strokes: a Pediatric Case Series

Background: MR-based vessel wall imaging (VWI) has gained influence in the clinical investigations, and management of pediatric strokes. Limitations still exist in interpreting it as a singular modality. Methods: We present 4 pediatric stroke cases with VWI enhancement. Results: Case 1. 4-year old boy with sickle cell anemia, who developed encephalopathy during a hemolytic crisis. MR-VWI revealed bilateral extracranial internal carotid enhanced narrowing, deemed a secondary vasculopathy, with resolution upon follow-up. Case 2. 16-year old male presented with left middle cerebral artery (MCA) infarction. VWI revealed left internal carotid terminus and proximal MCA enhancement. Conventional angiography showed abnormalities in mesentric and hepatic arteries. Stability sustained on anticoagulation and immunosuppressive therapy. Case 3. 10-year old girl, developed bilateral MCA infarctions with enhanced extracranial segments of both ICAs, and narrow PCAs, consistent with Moyamoya vasculopathy. Improved on combined immunosuppressive and anticoagulation therapy. Case 4. 13-year old boy had an episode of right facial weakness, with a normal neurological exam; with enhancement and narrowing in the left extracranial ICA, likely an intramural hematoma from dissection. He responded to dual anticoagulation therapy. Conclusions: In conclusion, these cases illustrate similarities in vessel wall imaging abnormalities under different clinical contexts, with practical utility in longitudinal follow-up and prognostication.

Reproducibility Between Three-Dimensional Turbo Spin-Echo and Two-Dimensional Dual Inversion Recovery Turbo Spin-Echo for Coronary Vessel Wall Imaging in Kawasaki Disease

Background: Magnetic resonance vessel wall imaging is desirable for evaluating Kawasaki disease (KD)-associated coronary arterial lesions. Purpose: To evaluate reproducibility of three-dimensional turbo spin-echo (3D-TSE) and two-dimensional dual inversion-recovery turbo spin-echo (2D-DIR-TSE) for coronary vessel wall imaging in KD.Methods: Ten patients were prospectively enrolled. Coronary vessel wall imaging with axial-slice orientation 3D-TSE and 2D-DIR-TSE were acquired for cross-sectional images in aneurysmal and normal regions. Lumen area (LA), wall area (WA), and normalized wall index (NWI) of cross-sectional images were measured in both regions. Reproducibility between 3D-TSE and 2D-DIR-TSE was evaluated via intraclass correlation coefficients (ICCs) and Bland-Altman plots.Results: 48 points (aneurysmal, 27; normal, 21) were evaluated. There were high ICCs between 3D-TSE and 2D-DIR-TSE in LA (0.95) and WA (0.95). In aneurysmal regions, 95% limits of agreement were LA, WA, and NWI of -29.9–30.4 mm2, -18.8–15.0 mm2, and -0.22–0.20, respectively. In normal regions, the 95% limits of agreement were LA, WA, and NWI of -4.44–4.38 mm2, -3.51–4.30 mm2, and -0.14–0.16, respectively. No fixed and proportional biases between 3D-TSE and 2D-DIR-TSE images in aneurysmal and normal regions were noted.Conclusions: 3D-TSE was reproducible with conventional 2D-DIR-TSE for coronary vessel wall assessment on KD.