Validity study of Spin Echo EPI based hepatic MR Elastography at 3.0T

Introduction: Magnetic Resonance Elastography (MRE), a noninvasive technique for quantitatively assessing the mechanical properties of soft tissues (1), is very promising for diagnosing hepatic fibrosis by detecting elevated hepatic shear stiffness (2-4). Typically MRE is performed on 1.5T MR systems as these are commonly available in the clinical practice. MR imaging at higher field strengths, specifically 3.0T, continues to be of significant interest because of the anticipated boost in intrinsic SNR at these field strengths. However, other effects like increased T1 and susceptibility can result in significant signal loss in GRE MRE that may affect the stiffness measurements. An alternative approach that may be more robust for performing MRE at higher field strengths is to use spin-echo EPI (SE-EPI) MRE, since the spin-echo properties of the signal may protect it against some of the susceptibility effects that affect GRE MRE. The purpose of this study was to evaluate a SE-EPI MRE protocol and compare it to a standard GRE MRE protocol at both 1.5T and 3.0T in healthy volunteers with no known liver disease to determine if the signal variations characteristic of the different imaging sequences and field strengths cause a significant change in the SNR of the data or adversely affect the estimates of tissue stiffness.