Time-resolved three-dimensional (3D) phase-contrast (PC) balanced steady-state free precession (bSSFP)

In this study the feasibility of a time-resolved, three-dimensional (3D), three-directional flow-sensitive balanced steady-state free precession (bSSFP) sequence is demonstrated. Due to its high signal-to-noise ratio (SNR) in blood and cerebrospinal fluid (CSF) this type of sequence is particularly effective for acquisition of blood and CSF flow velocities. Flow sensitivity was achieved with the phase-contrast (PC) technique, implementing a custom algorithm for calculation of optimal gradient parameters. Techniques to avoid the most important sources of bSSFP-related artifacts (including distortion due to eddy currents and signal voids due to flow-related steady-state disruption) are also presented. The technique was validated by means of a custom flow phantom, and in vivo experiments on blood and CSF were performed to demonstrate the suitability of this sequence for human studies. Accurate depiction of blood flow in the cerebral veins and of CSF flow in the cervical portion of the neck was obtained. Possible applications of this technique might include the study of CSF flow patterns, direct in vivo study of pathologies such as hydrocephalus and Chiari malformation, and validation for the existing CSF circulation model.