Fig. 2

Pulse sequence diagram for Cartesian 4DFlow showing the gradients for (a) single TR and the combination of these encodings for ECG gated sampling (b). For each phase encoding, four measurements are taken with separate velocity encodings. As shown, one image is acquired with flow compensation and subsequent velocity encodings are acquired on the x (red), y (blue) and z (green) axes. In order to tradeoff temporal resolution for scan time, it is common to acquire cardiac frames with view sharing. In this case 3 lines of k-space are collected per cardiac trigger resulting in a temporal resolution of 12 TRs