Characterization of Arterial and Sinus Blood Flow Dynamics in the Rat Brain Using Phase-Contrast MRI

Phase-contrast magnetic resonance imaging (PC-MRI) is a widely used technique for measuring cerebral blood flow dynamics in humans. However, the application of this technique for velocity mapping of cerebral blood flow in rats has been very limited thus far. This study aimed to determine the accuracy of PC-MRI flow measurements and to establish reference flow values for the main intracerebral feeding and draining vessels in rats. PC-MRI velocimetry was conducted on a flow phantom and 12 adult Sprague Dawley rats. A semi-automatic segmentation was applied to the velocity images to enable the quantification of flows and the calculation of pulsatility index. PC-MRI flow measurements showed good agreement with the reference flow from the pump. The main findings of the in vivo measurements were as follows: the mean blood flow values in the internal carotid artery (ICA), external carotid artery (ECA), basilar artery (BA), and transverse sinuses were 9.6 ± 3.4, 5.7 ± 2.4, 2.0 ± 0.6, and 10.5 ± 3.6 ml/min, respectively. Mean ICA flow was higher than ECA flow, while the ICA pulsatility index was lower than the ECA pulsatility index. There was no significant difference in the mean cerebral inflow (combined ICA and BA flows) and cerebral outflow (left and right transverse sinus flows) measures. No differences in arterial or sinus flow were observed between the left and right sides of the brain. These reference flow values and pulsatility index may be useful for understanding flow dynamics in healthy and pathological conditions in rats.