Signal behavior in continuously ramped 2D TrueFISP for whole-body imaging

A fast and robust imaging technique was developed based on a single-slice TrueFISP acquisition using a slice excitation frequency that is incremented, or spatially "ramped," with each repetition. The short acquisition time of single slices allows artifact-free imaging during free breathing, which demonstrates the potential use of this technique for whole-body screening. Overlapping positioning of consecutively acquired slices was used to provide gapless volume coverage in free-breathing measurements. The image contrast of ramped TrueFISP was analyzed in detail using simulations and experiments. A high ramp speed results in an increased overall signal intensity and in a modification of the known T(2)/T(1) contrast towards a proton density-weighted contrast. A further increase in imaging speed is achieved with z-interleaved phase-encoding trajectories based on weighted transitions between adjacent views.