Posture Dependence of Cerebral Spinal Fluid and Blood Flow by Phase Contrast Magnetic Resonance Imaging at 3 T

Understanding how body posture influence the cerebrospinal fluid (CSF) and blood flow is crucial for developing effective treatment strategies for neurological diseases. 2D phase contrast (PC) MRI is commonly used to investigate flow dynamics in the cerebral aqueduct (CAq) and large blood vessels. However, the measured results are susceptible to head motion and variation in slice locations between postures. We developed a PC-MRI sequence incorporating prospective motion correction (PMC) and consistent slice prescription. Using this sequence, we investigated blood and CSF dynamics in young healthy adults in supine and prone postures. Stroke volumes, flow velocities, absolute flows, and cross-sectional areas of the CAq, internal carotid artery (ICA), vertebral artery, internal jugular vein (IJV), superior sagittal sinus, and straight sinus were measured in 14 healthy volunteers in both postures. Compared to the supine posture, we found no significant change in blood flow in any blood vessels in the prone posture, but the ICA (p = 0.009) and IJV (p = 0.049) stroke volume significantly decreased. Meanwhile, the absolute flow (p = 0.005), stroke volume (p = 0.001), and velocity variation range  $V_{\text{range}}$ (p = 0.002) of the CAq significantly decreased in the prone posture. There were significant positive correlations between the posture-induced stroke volume changes of CAq and ICA (ρ = 0.55, p = 0.044) and of IJV and ICA (ρ = 0.76, p = 0.016). The cardiac phase dependent changes in flow velocities were also strongly correlated between CAq and ICA. These findings suggest a close coupling between blood flow and CSF dynamics and a reduction of CSF circulation during prone posture. The developed sequence will facilitate longitudinal monitoring of vascular and CSF flow properties during the pathogenesis of neurovascular diseases.