Figure 1.

Schematic excitation and acquisition diagram of the free breathing interleaved multi-echo UTE (FB-imUTE) sequence, only important elements are shown: Prior to each half pulse (abbreviated as HP in diagram) excitation, CHESS pulses for fat suppression and sSAT pulses for out-of-slice signal suppression are applied. CHESS and sSAT pulses are followed by spoiler gradients (not shown) to dephase transverse magnetization. The sSAT bands are oriented in parallel to the imaging slice. The slice selection (G_SL, light gray; dotted line indicates alternating polarity of slice selection gradients) and readout (G_RO, dark gray) gradients are illustrated for the first echo train only. Each echo of the multi-echo readout train is acquired via center-out radial sampling including data acquisition during ramp-up of the readout gradients. The sequence acquires additional echo trains which are shifted relative to the previous echo train by a small echo time increment ΔTE to achieve dense temporal sampling even for fast T2* decay.