(Thursday, 7/18/2019) 7:30 AM - 9:30 AM
Room: 303
Purpose: Several groups have investigated the role of magnetic resonance elastography (MRE) for the diagnosis of neurological diseases primarily using 2D imaging acquisitions. The objective of this study was to determine the feasiblity of incorporating 3D GRE (Gradient Recalled Echo) MRE into routine brain MR imaging examinations on a compact 3T (C3T) scanner with high-performance gradients.
Methods: Twelve healthy volunteers and 9 patients with tumors (recruited under IRB-approved protocols) were imaged with 3D GRE MRE after providing written informed consent. A 3D sagittal MRE exam was performed on a compact 3T scanner (maximum: gradient amplitude=80 mT/m, slew rate=700 T/m/s) with the following acquisition parameters, 72 mT/m motion encoding gradients (MEG), mechanical vibration=60Hz, TE=20.4ms, TR=24.1ms, one MEG cycle with zeroth- and first- moment nulling, BW=±25kHz, FOV = 240x240x192mm3, acquisition matrix=120x120x96, resolution = 2x2x2mm3, flip angle = 12, scan time=12:25. Real-time gradient pre-emphasis and frequency shifting compensated additional concomitant fields from the asymmetric gradient design. One healthy volunteer was also scanned twice on a standard clinical 3T scanner (Signa HDxt, GE Healthcare) for comparison.
Results: The shear wave displacement sensitivity between the C3T and conventional 3T scanner is shown in Figure 1. The C3T has the SNR and motion sensitivity necessary to capture shear wave amplitudes, but the conventional whole body 3T scanner (maximum: gradient amplitude=34 mT/m and slew rate=200 T/m/s) does not. 3D FGRE MRE elastograms and magnitude images in a patient with a small meningioma are shown in Figure 2. This exam demonstrates the feasibility of measuring tissue stiffness within tumors and the MRE soft characterization of the tumor was congruent with the surgical findings.
Conclusion: This study demonstrated that the C3T scanner has sufficient gradient performance to successfully acquire high resolution 3D GRE MRE exams in patients and healthy controls, which is not possible on a conventional 3T scanner.
Funding Support, Disclosures, and Conflict of Interest: All conflicts of interest have been reviewed by the Mayo Clinic Conflict of Interest Review Board and is being conducted in compliance with Mayo Clinic Conflict of Interest policies.
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