Yi Sui^{1}, Arvin Arani^{1}, Joshua D. Trzasko^{1}, Shivaram P. Arunachalam^{1}, Kevin J. Glaser^{1}, Kiaran P. McGee^{1}, Phillip J. Rossman^{1}, Armando Manduca^{1}, Richard L. Ehman^{1}, John Huston III^{1}, and Philip A. Araoz^{1}

A 3D gradient-echo EPI MR Elastography pulse sequence has been developed using a hybrid radial-Cartesian readout scheme, named Trajectory Using Radially Batched Internal Navigator Echoes (TURBINE). The feasibility of this TURBINE-MRE sequence was demonstrated in a phantom study.

**Introduction**

**Results**

Figure 2 shows the first harmonic of the 3D wave images obtained from the TURBINE-MRE and SE-EPI-MRE phase images. Coronal and axial views are shown. Of note, TURBINE-MRE is a true 3D acquisition, whereas SE-EPI-MRE is a multislice acquisition which produces a stack of 2D images.

Figure 3 shows the stiffness maps calculated using a local-frequency estimation algorithm (LFE) (10) for the two sequences. The mean stiffness from TURBINE-MRE and SE-EPI-MRE in the ROI (black circle) was 5.2±0.5 kPa and 5.1±0.4 kPa, respectively.

**Discussion and Conclusion**

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Figure 1. (a) Pulse sequence diagram for TURBINE-MRE. The MEG can be applied in the x, y, and/or z directions to record the full vector wave motion. The MEG and the mechanical vibration are temporally shifted relative to each other by the φ in different acquisitions to acquire different phases of the harmonic motion. G_{SS/PE} represents the slab-selection axis and EPI phase-encoding direction. G_{θ} represents the readout axis rotating about the G_{SS/PE} axis in successive TRs. (b) The 3D TURBINE k-space trajectory. An EPI readout (blade) is acquired in each TR. Successive EPI readouts are rotated along the G_{SS/PE} axis (k_{z} in this case) to fill the k-space.

Figure 2. Coronal and axial views of the wave images obtained from the TURBINE-MRE and SE-EPI-MRE phase images. Note that TURBINE-MRE is a true 3D acquisition, whereas SE-EPI-MRE is a multislice acquisition which produces a stack of 2D images.

Figure 3. The stiffness maps calculated using a local-frequency
estimation (LFE) algorithm for the TURBINE-MRE and SE-EPI-MRE acquisitions. The
mean stiffness from TURBINE-MRE and SE-EPI-MRE in the ROI (black circle) was 5.2±0.5
kPa and 5.1±0.4 kPa, respectively.