The main window of cardioGRAF^® processing the electrocardiogram-gated myocardial perfusion single photon emission computed tomography (SPECT) in a healthy subject. The division of the left ventricular myocardium into 17 volume segments and numbering are illustrated on the upper right panel. The upper left panel displays the time–volume curves of the segments. The time 0 on the abscissa is triggered on the peak of the R-wave that is not shown here. The lower left panel shows the derivative of the time–volume curves that corresponds to the contraction velocity of the respective volume segment. The vertical dotted lines on the time–volume curves are the instant of end systole of each regional myocardial volume estimated by zero-crossing of contraction velocity and minimal volume.