Navigator echoes in cardiac magnetic resonance.

Navigator echoes are frequently used in cardiac magnetic resonance to monitor respiratory motion and have proved particularly useful in coronary artery imaging techniques where they allow the acquisition of data over multiple reproducible breathholds and during free breathing. The large number of variables involved in their use, however, is such that an optimal method of application may yet have to be developed. In this review article, we examine the issues relating to their implementation and describe the ways in which the navigator information obtained may be used.