Secondary to acute ischemic stroke, evolving dysfunctions in small vessels play a critical role in exacerbating tissue damage and cognitive decline. However, reliable in vivo tools for studying brain microvasculature over time are scarce, and existing methods must be adapted to experimental conditions that vary temporally. This is particularly true for magnetic resonance imaging (MRI)-based protocols to assess microvascular hemodynamics in living mice.

Ischemic stroke can lead to significant alterations in the vascular network, especially at later stages, when processes such as vascular remodeling and atrophy occur. Consequently, structural data from existing literature may not provide accurate approximations, making it necessary to obtain direct structural information on murine ischemic neurovascular damage.

To address this, we developed an experimental approach that integrates high-resolution morphological techniques, such as Synchrotron X-ray phase contrast tomography, with in vivo MRI (Diffusion, Morphometry and Intravascular Incoherent Motion, IVIM). We analyzed brains collected at different time points —baseline, 1, 7, and 35 days— after an ischemic insult by 30-minute occlusion of the middle cerebral artery or after sham surgery. X-ray tomography allowed the visualization of unlabeled small vessels (order of 10 micron) pertinent to the ischemic area, which was identified using aligned MRI morphometric images. This combination enabled the extraction of vessel structural information, offering useful parameters to refine algorithms for microvascular hemodynamics by IVIM.

Our results pave the way for longitudinal analysis of small vessel dysfunctions in the intact brain, with the final goal of linking cognitive decline to microvascular pathological changes.