Motion detection from the measured signals in magnetic resonance imaging

We present a new quantitative method to determine motion intervals in projection reconstruction (PR) magnetic resonance imaging. The method does not use any a priori information concerning the motion. In the first section, the theoretical concept of the method is described. It is shown that the phase of the complex mean of a one-dimensional PR signal equals zero when no motion is present. When the depicted object is moving, it differs from zero. These conclusions are used to determine motion intervals from the raw PR data. The motion-detection method proves to be able to detect motion intervals with an accuracy of one repetition time.