FIGURE 2.

Basic principle of HYFI acquisition to avoid strong discontinuities in the recorded signal amplitudes. Due to T ₂* relaxation, the MR signal s decays exponentially over time. With the zero echo time (ZTE) sequence of Figure 1A, acquisition starts after the dead time Δt. In HYFI, any subsequent data collection for the inner k‐space is restricted to an acquisition time t_acq in order to limit signal amplitudes to a given range R. Normalization of R by the signal amplitude at the dead time s(Δt) provides the amplitude coefficient A. In practice, a target T ₂* and A are selected and t_acq follows from the given equation