Multi-point velocity encoding for simultaneous assessment of arterial, venous and cerebrospinal flow

Introduction: The acquisition of arterial and venous blood flow to the cranium as well as flow of cerebrospinal fluid (CSF) in the spinal canal are the main input parameters for modeling cerebrospinal dynamics [1]. Phase-Contrast (PC) MRI has been used to measure input and output boundary conditions to populate model parameters. There are, however, limitations as to the accuracy of PC-MRI when mapping arterial influx and venous outflow with conventional phasecontrast methods. While arterial blood enters the scull in feet-head direction through the common carotid (CCA) and vertebral arteries (VA), the venous system is geometrically more complex without a well-defined principal axis of flow and with large inter-subject variation [2]. The jugular (JV) and vertebral veins are accompanied by collateral pathways that can be numerous, small in diameter and along various orientations. Arterial inflow and venous outflow is often measured using the method introduced by Alperin [3]. According to this method, arterial blood flow and flow in the jugular vein are measured over one cardiac cycle with two PC-MRI acquisitions with high and low velocity encoding. As net arterial blood flow has to equal net venous blood flow, venous blood flow is scaled up to match arterial inflow. The simultaneous acquisition in a dual venc approach has been proposed in order to detect velocity information at the same time points [4]. Despite dual venc acquisition, velocity sensitivity might still be insufficient when attempting flow measurements in the venous system beyond the jugular veins. The present study aimed at simultaneous measurement of arterial, venous and CSF flow in the neck using a multi-point variable-density velocity encoded 3D sequence with spatiotemporal undersampling.