1. A magnetic resonance (MR) imaging apparatus comprising: an MRI system having components including static and gradient magnetic field generators, at least one radio frequency (RF) coil coupled to an imaging volume, at least one RF transmitter, at least one RF receiver and at least one control computer having a processor and memory configured to control said system components so as to effect: Time Spatial Labelling Inversion Pulse (Time-SLIP) acquisition of MR image data by repeating an imaging process a plurality of times in synchronization with a trigger signal, the imaging process including application of a labelling pulse to Cerebrospinal Fluid (CSF) flowing inside a subject, and thereafter collecting a magnetic resonance (MR) echo signal after application of an MR excitation pulse to an imaging region including the CSF; creation of a plurality of images of labelled CSF based on echo signals collected by said repetition of the imaging process; creation of an average value image based on the plurality of images; and calculation of variance of signal strengths with respect to each of same positions on the plurality of images based on (a) the plurality of images and (b) the average value image.