Effect of Cardiac- and Respiratory-driven Tissue Motion on Microscopic Velocity Measurement of Neurofluid based on Complex-valued Propagator

Motivation: To investigate how pulsatile tissue motion induced by heartbeat and respiration influence on measurement of neurofluid velocity, which is far slower than the pulsatile motion. Goal(s): Quantitative visualization of microscopic neurofluid velocity in the brain using propagator analysis based on Q-space imaging (QSI). Approach: Numerical analysis based on Bloch-Torrey method, which simulated our pervious mouse experiments, were conducted to clarify the effect of pulsatile motions on the propagator obtained by QSI in cases with and without additional pulsatile tissue motion. Results: The pulsatile motion distorted propagator lobe shape. However, the change of the propagator peak position indicating the microscopic velocity was relatively minor. Impact: The results implies that the QSI-based quantitative visualization of neurofluid velocity is feasible even under pulsatile tissue motion occurring in the brain. Such quantitative technique will make one step further to elucidate the mechanism of neurowaste clearance system.