Longitudinal MR angiographic evaluation of circle of Willis morphologic remodeling and induced aneurysms in Hashimoto rat cerebral aneurysm model

We aimed to longitudinally characterize morphological remodeling of the Circle of Willis (COW) and aneurysm development in the Hashimoto rat cerebral aneurysm model using serial high-resolution 7T MR imaging. Aneurysm induction was achieved through unilateral carotid and renal artery ligation combined with salt and β-aminopropionitrile loading to induce hemodynamic stress and vascular fragility. TOF-MRA, T2-weighted, and black-blood MR sequences were acquired at four time points over 12 weeks. Morphological changes were quantified by measuring arterial diameters and tortuosity indices. Postmortem scanning electron microscopy (SEM) following vascular corrosion casting was used as the diagnostic reference. Significant asymmetric vascular remodeling was observed predominantly in the posterior circulation, with fusiform aneurysms confirmed by SEM in the left PCA P1 segment in two cases, both associated with subarachnoid hemorrhage. Microaneurysms below MR detection threshold were found at ACA–OA and ICA–MCA bifurcations. The sensitivity and specificity of MR-based aneurysm detection were 40% and 60%, respectively. While spatial resolution limited visualization of smaller lesions, longitudinal MR imaging allowed dynamic tracking of vascular changes and provided insight into early aneurysmogenesis. This platform enables in vivo evaluation of aneurysm initiation, growth, and rupture risk, supporting its potential utility for preclinical assessment of therapeutic strategies.