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. Author manuscript; available in PMC: 2008 Sep 1.
Published in final edited form as: Methods. 2007 Sep;43(1):35–45. doi: 10.1016/j.ymeth.2007.03.012

Figure 4.

Figure 4

A timing diagram for a cine MRI acquisition using a spoiled gradient echo (GRE) pulse sequence gated to the R-wave of the ECG signal. For the GRE sequence diagram (bottom), RF refers to the radiofrequency signal and shows both the excitation pulse (α) and the resulting MR signal or echo. Slice-select (SS), phase encode (PE), and readout (RO) gradients are used to selectively acquire the signal for a two-dimensional imaging slice. The echo time (TE) is a standard MRI parameter defined as the time between the excitation flip angle and the MR signal. The repetition time (TR) is the time between excitation RF pulses and determines the temporal resolution. Individual images are acquired at different phases (e.g. 1,2,3,4,5,6,…) of the cardiac cycle. The maximum number of cardiac phases that can be acquired is determined by the TR and the time interval between R waves of consecutive heart beats. The phase encoding gradient is incremented over multiple heart beats to acquire a complete image.