Schematic illustration of the method. Low-res images are stacked along the time dimension (a). One cross-section through the 3D spatial-temporal volume shows a 2D image in the x-t plane (b). If the pixels are static over time (profile p2), the x-t image would exhibit horizontal and vertical structures, while a profile going through the myocardium (profile p1) with moving objects along the time dimension, would show more inhomogeneous structures, thus generating a pattern with breathing motion information (c). The extracted respiratory signal (red) shows good agreement with the respiratory belt (blue), with a coefficient of determination R2 = 0.76.