A method of compensating for motion artefact of a portion of a subject, wherein signal intensity data representing movement of the portion of the subject is recorded and plotted on a display means. The method includes selecting a region of interest (ROI) covering an edge of the moving portion, calculating and plotting data points representing the average signal intensity of the selected ROI at specific time instances, producing a smoothed curve representing the mean of the plotted data points. The method further includes measuring the difference between the plotted data points and the smoothed curve at particular time instances to produce a difference curve, detecting a set of critical points on the difference curve, and interpolating the detected set of critical points to form a curve of equal time intervals for subsequent processing.