Evaluation of Cerebral blood flow dynamics in rat brain using Phase contrast MRI. Technical challenges and physiological consideration

(max 200 words): The cranium is a rigid structure that encloses the brain parenchyma, arterial and venous blood, and cerebrospinal fluid (CSF), all sharing a non-expandable space. This anatomical constraint requires a regulated balance between cerebral blood supply and CSF oscillations to maintain adequate intracranial pressure. In several brain disorders, studies have reported the involvement of these circulations and their interactions with the glymphatic network. The rat, widely used in neuroscience, shares important similarities with the human brain, making it a suitable model for investigating cerebral blood flow dynamics. However, no study has yet specifically examined the arterial and venous contributions to cerebral circulation in detail. In this study, we used phase-contrast magnetic resonance imaging (PC-MRI), the only non-invasive technique that enables a detailed assessment of both arterial inflow and venous outflow within minutes. Eight rats were anesthetized with isoflurane, and three optimized imaging planes were acquired to capture venous and arterial structures. Preliminary results showed a strong correlation between arterial inflow and venous outflow (R = 0.851, p = 0.007), indicating arterio-venous coupling and confirming the consistency of the acquired data. Considerable inter-individual variability was observed on the venous side, which may be related to physiological and the limits of the approach. these findings demonstrate that PC-MRI provides a reliable non-invasive method to assess arterio-venous interactions in the rat brain