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

## TL;DR

This study uses MR imaging to track vascular changes and aneurysm development in a rat model over time, providing insights into aneurysm formation and potential therapeutic evaluation.

## Contribution

The study introduces a longitudinal MR imaging platform for in vivo evaluation of aneurysm initiation and growth in a rat model.

## Key findings

- Significant asymmetric vascular remodeling was observed in the posterior circulation of the rat model.
- Fusiform aneurysms were confirmed in the left PCA P1 segment, associated with subarachnoid hemorrhage.
- Longitudinal MR imaging enabled dynamic tracking of vascular changes despite limitations in detecting smaller lesions.

## Abstract

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.

The online version contains supplementary material available at 10.1038/s41598-026-37369-2.