Magnetization preparation during the steady state: fat-saturated 3D TrueFISP

Abstract

A novel fat saturation scheme is proposed which combines spectral fat saturation with a steady-state 3D true Fast Imaging with Steady Precesson (TrueFISP) sequence. Fat saturation consisted of a conventional frequency-selective excitation pulse surrounded by spoiler gradients. This saturation block was periodically repeated within a continuously running TrueFISP sequence. Except for the fat signals, the steady-state signal formation and the resulting image contrast of TrueFISP was not modified by the periodically inserted fat saturation block. This was achieved by a alpha/2 flip-back pulse before the fat saturation block, which stores the established steady-state transverse magnetization as pure longitudinal magnetization. After fat saturation this longitudinal magnetization was excited by a alpha/2 preparation pulse to continue the TrueFISP acquisition. The resulting images show contrast identical to conventional TrueFISP images, but without the usually very bright fat signals. The short repetition time allows acquisition of a 3D data set of the abdomen within a single breath-hold.