Left ventricular volume graphs from Wiggers diagram demonstrating optimal trigger delays for single-phase cardiac MRI. (a) Minimal systolic motion begins during the last 1/6 of LVET, when the left ventricular volume change is small. Tsys = IVC + 5/6 LVET, where LVET = QS2 - QonsetRpeak - IVC. (b) Minimal diastolic motion begins slightly before the end of the rapid filling phase. Tdias = QS2 - QonsetRpeak + IVR + Trapid - 50.