Brain and cerebrospinal fluid motion: real-time quantification with M-mode MR imaging.

Abstract

To assess motion of brain parenchyma and cerebrospinal fluid (CSF) with magnetic resonance (MR) phase imaging in real time. Repetitive excitation of a cylinder with two-dimensional selective excitation followed by one-dimensional imaging along the cylinder axis yielded profiles analogous to those of M-mode echography. Bipolar gradients provided velocity sensitivity in an arbitrary spatial direction. Brain and CSF of healthy volunteers exhibited periodic motion in the frequency range of normal heart rate. Both brain hemispheres showed periodic squeezing of the ventricles, with peak velocities up to 1 mm/sec followed by a slower recoil. Superimposed on the regular displacement of the brain stem was a slow, respiratory-related periodic shift of the neutral position. During the Valsalva maneuver, the brain stem showed initial caudal and subsequent cranial displacement of 2-3 mm. Coughing produced a short swing of CSF in the cephalic direction. Real-time MR phase imaging allows observation of non-periodic events in brain and CSF motion.