Patient-Activated Three-Dimensional Multifrequency Magnetic Resonance Elastography for High-Resolution Mechanical Imaging of the Liver and Spleen

Abstract

Purpose: To introduce a novel in-vivo three-dimensional multifrequency magnetic resonance elastography (3D-MMRE) method for high-resolution mechanical characterization of the liver and spleen. Materials and Methods: Ten healthy volunteers were examined by abdominal single-shot 3D-MMRE using a novel patient-activated trigger system with respiratory control. 10 contiguous slices with 2.5?mm cubic voxel resolution, 3 wave components, 8 time steps, and 2 averages were acquired at 7 mechanical excitation frequencies from 30 to 60?Hz. The total imaging time was approximately 15?min. For postprocessing, multifrequency dual elasto-visco (MDEV) inversion was used to calculate high-resolution mechanical parameter maps of the abdomen including the liver and spleen. Results: Two parameters maps were generated from each image slice to capture the magnitude and the phase angle of the complex shear modulus. Both parameters depicted the mechanical structures of the abdomen with unprecedented high spatial resolution. Spatially averaged group mean values of the liver and spleen are 1.27???0.17 kPa and 2.01???0.69 kPa, indicating a significantly higher asymptomatic stiffness of the spleen compared to the liver. Conclusion: Patient-activated respiratory-gated 3D-MMRE combined with MDEV inversion provides highly resolved mechanical maps of the liver and spleen that are superior to previous elastograms measured by abdominal MRE. Citation Format: ??Guo J, Hirsch S, Streitberger KJ et?al. Patient-Activated Three-Dimensional Multifrequency Magnetic Resonance Elastography for High-Resolution Mechanical Imaging of the Liver and Spleen. Fortschr R?ntgenstr 2014; 186: 260???266

Elasticity mapping of murine abdominal organsin vivousing harmonic motion imaging (HMI)

“…Moreover, definite conclusions on healthy abdominal organs relative stiffness remains to be determined. Across the literature and the different elastography techniques, the liver is commonly found to be relatively soft with a Young’s modulus between 5 and 10 kPa (Bensamoun et al 2011; Castera et al 2010; Guo et al 2014; Masuzaki et al 2007; Palmeri et al 2008; Yin et al 2007a), when the kidney is admitted to be stiffer (Arda et al 2011; Bensamoun et al 2011; Gallotti et al 2010; Gennisson et al 2012) as observed in this study. However the stiffness of the spleen and the pancreas are not as well established.…”

“…Using SWE in healthy volunteers, Arda et al (Arda et al 2011) showed that the spleen was softer (2.9 ± 1.8 kPa) than the pancreas (4.8 ± 3 kPa), when Leung et al (Leung et al 2013) found the spleen to be much stiffer (17.3 ± 2.6 kPa) than the liver (5.5 ± 0.7 kPa). Results from different ARFI studies also measured a higher stiffness in the spleen than in the liver (Cabassa et al 2015; Guo et al 2014), the pancreas and even the kidney (Gallotti et al 2010). More studies are needed to draw conclusions on the relative stiffness of abdominal organs both in human and small animal.…”

In vivo high-resolution magnetic resonance elastography of the uterine corpus and cervix

“…For MRE parameter recovery, we used the MDEV inversion algorithm proposed earlier [11,14] which provides two independent parameters, |G * | and φ, corresponding to the magnitude and the phase angle of the complex shear modulus G * . Compared with the previous work, we modified the reconstruction algorithm in a way that (i) six in-plane derivative components u j,k were used for inversion instead of three curl components and (ii) instead of solving an over-determined set of equations MA=B for M by MA T A=A T B (T denotes the vector transpose) we considered the unweighted average, i.e.…”

“…Using this technique, highly resolved maps of the magnitude (|G * |) and the phase angle (φ) of the complex shear modulus were obtained in the liver and spleen [11,14], the kidney [14] and the brain [15]. |G * | combines both elasticity and viscosity and therefore relates to the haptic material properties; φ quantifies the degree of fluidity, i.e.…”

Multifrequency Time-Harmonic Elastography for the Measurement of Liver Viscoelasticity in Large Tissue Windows

“…Total scan time was approximately 6 min. Parameter reconstruction was based on multifrequency dual elasto-visco inversion as proposed in Guo et al (2014) and Hirsch et al (2013), yielding the magnitude (jG Ã j) and the phase angle (4) of the complex shear modulus of the liver. For comparison to THE, both parameters were converted to shear wave speed using…”