Fig. 1.

Timing diagram for the 3D cine DENSE pulse sequence. A navigator echo is played out before the ECG trigger so as not to interfere with displacement encoding prior to or imaging during the onset of myocardial contraction (marked as the NAV block in the diagram). Immediately after detection of the R wave, a spectrally-selective fat suppression pulse is applied (marked as the FS block in the diagram), which is followed by the displacement-encoding module. A segmented data acquisition, which includes displacement-unencoding gradients and a 3D stack-of-spirals k-space trajectory, is used to sample the displacement-encoded longitudinal magnetization at multiple cardiac phases. In this diagram, the displacement-encoding gradients are applied in the frequency-encoding direction (the gradient waveform shown in the solid line on the G_FE axis). However, more generally, displacement encoding can be applied in any direction by also applying the gradients shown in dashed lines on the G_PE and/or G_SS axes, respectively. Applying gradients in multiple directions is employed for balanced multi-point displacement encoding. In practice, to minimize the echo time, the displacement-unencoding gradients are combined with spatial encoding gradients, but are shown separately in this diagram for clarity.