Phase-Contrast MRI Detection of Ventricular Shunt CSF Flow: Proof of Principle

The evaluation of a suspected malfunction of a ventricular shunt is a common procedure in neurosurgery. The evaluation relies on either the interpretation of the ventricular width using cranial imaging or invasive techniques. Several attempts have been made to measure the flow velocity of cerebrospinal fluid (CSF) utilizing different phase-contrast magnet resonance imaging (PC MRI) techniques. In the present study, we evaluated 3 T (Tesla) MRI scanners for their effectiveness in determining of flow in the parenchymal portion of ventricular shunt systems with adjustable valves containing magnets.

At first, an MRI phantom was used to measure the phase-contrasts at different constant low flow rates. The next step was to measure the CSF flow in patients treated with ventricular shunts without suspected malfunction of the shunt under observation.

The measurements of the phantom showed a linear correlation between the CSF flow and corresponding phase values. Despite many artifacts resulting from the magnetic valves, the ventricular catheter within the parenchymal portion of shunt was not superimposed by artifacts at each PC MRI plane and clearly distinguishable in 9 of 12 patients. Three patients suffering from obstructive hydrocephalus showed a clear flow signal.

CSF flow detected within the parenchymal portion of the shunt by PC MRI may reliably provide information about the functional status of a ventricular shunt. Even in patients whose hydrocephalus was treated with magnetic adjustable valves, the CSF flow was detectable using PC MRI sequences at 3 T field strength.