Improved Navigator Performance by Parallel Transmission

Manuel Walther¹, Kay Nehrke², Ingmar Grsslin², Ulrich Katscher², Markus Eblenkamp¹, Erich Wintermantel¹, Peter Brnert²

Parallel transmission has been used to overcome B1 homogeneity limitations and to improve the performance of multi-dimensional RF pulses by shortening their duration. One of the simplest multi-dimensional RF pulses is the pencil beam which finds application as a navigator to sense respiratory motion. As modern high-field systems (3T and beyond) are especially prone to off-resonance effects, shorter pulse durations are necessary to overcome this problem. However, accelerated pulses also cause aliasing artifacts. Transmit SENSE, replacing gradient encoding with transmit sensitivity encoding, has been found to significantly improve the performance of these accelerated navigator pulses, allowing pulse durations of 1.7ms.