Figure 14a.

Respiratory motion compensation with a navigator sequence. (a, b) Coronal gradient-echo MR images obtained without (a) and with (b) respiratory synchronization by using a navigator sequence. (c) Coronal MR image shows the result of using the navigator sequence; the green rectangle demonstrates placement of an additional pulse to excite magnetization over the diaphragm, which allows a one-dimensional real-time tracing of diaphragmatic excursion. From this information, imaging can be timed prospectively or reconstructed retrospectively to minimize motion related to respiration.