Double Half RF pulses for reduced sensitivity to eddy currents in UTE imaging

Abstract

Ultrashort echo time imaging with half RF pulse excitation is challenging as eddy currents induced by the slice-select gradient distort the half pulse slice profile. This work presents two pulses with T2-dependent slice profiles that are less sensitive to eddy currents. The double half pulse improves the slice selectivity for long T2 components, while the inverted double half pulse suppresses the unwanted long T2 signal. Thus, both approaches prevent imperfect cancellation of out-of-slice signal from contaminating the desired slice. Experimental results demonstrate substantially improved slice selectivity and R2* quantitation accuracy with these pulses. These pulses are effective in making short T2 imaging and quantitation less sensitive to eddy currents and provide an alternative to time-consuming gradient characterization. © 2009 Wiley-Liss, Inc.