Pulse sequence diagram. The first portion of the pulse sequence is tagging, where the magnetization is modulated in the z-direction right after the detection of the R-wave of the electrocardiogram (ECG). Later at the imaging timepoint, three images are consecutively acquired (18 ms apart) with three radiofrequency (RF) pulses (αNT, αLT, and αHT) and three demodulation gradients (NT, LT, and HT) in the z-direction. Spiral acquisition is used for signal readout. The magnetization then recovers until the next cardiac cycle. NT = no-tuning; LT = low-tuning; HT = high-tuning; and TR = repetition time.