Figure 1a. Techniques of retrospective image reconstruction. (a) ECG strip shows the relative delay method, in which a certain delay from the prior wave is determined as a percentage of the R-R interval. This delay is used to start reconstruction. (b) ECG strip shows the absolute delay method, in which a fixed time delay after the R wave determines the start of reconstruction. (c) ECG strip shows the absolute reverse method, in which a fixed time before the next R wave determines the start of reconstruction.