[Estimating intracranial fluid dynamics using quantitative analyses of phase contrast magnetic resonance images]

Abstract

Objective: To estimate the dynamic relations between cerebrospinal fluid (CSF) and blood in the cerebral and spinal subarachnoid spaces and in the ventricles by quantifying phase contrast magnetic resonance imaging (MRI).

Material and methods: We analyzed 15 healthy volunteers during the same time of day and using the same magnetic field strength (3T). Each study consisted of four phase contrast sequences: two to calculate the CSF (aqueduct of Sylvius and the C2-C3 perimedullary space) and two to calculate the blood flow (internal carotid and vertebral arteries, superior sagittal sinus, and straight sinus). We calculated the amplitude parameters (systolic volume, mean flow, pulsatility and compliance indexes, absolute pressure gradient, and ratio of CSF volume per cycle) and temporal parameters (delays respect to arterial flow).

Results: With respect to the input of arterial blood, the displacement of venous blood (22% and 38% of the cardiac cycle in the straight sinus and superior sagittal sinus, respectively) and of CSF (12% and 25% of the cardiac cycle in the C2-C3 perimedullary space and in the aqueduct of Sylvius, respectively) show the distribution of the pulsatility of the intracranial fluids. We calculated the indexes of compliance of the encephalic and medullary compartments in normal subjects.

Conclusions: It is possible to quantitatively describe the dynamic relations between intracranial fluids and infer the elastic behavior of the brain and spinal canal by using flow velocity maps obtained with phase contrast MRI.