Radiofrequency Pulses for Simultaneous Short T2 Excitation and Long T2 Suppression

Magnetic resonance imaging of short T-2 musculoskeletal tissues such as ligaments, tendon, and cortical bone often requires specialized pulse sequences to detect sufficiently high levels of signal, as well as additional techniques to suppress unwanted long T-2 signals. We describe a specialized radiofrequency technique for imaging short T-2 tissues based on applying hard 180 degrees radiofrequency excitation pulses to achieve simultaneous short T-2 tissue excitation and long T-2 tissue signal suppression for three-dimensional ultrashort echo time applications. A criterion for the pulse duration of the 180 degrees radiofrequency pulses is derived that allows simultaneous water and fat suppression. This opens up possibilities for direct imaging of short T-2 tissues, without the need for additional suppression techniques. Bloch simulations and experimental studies on short T-2 phantoms and specimen were used to test the sequence performance. Magn Reson Med 65:531-537, 2011. (C) 2010 Wiley-Liss, Inc.