K-space data processing for magnetic resonance elastography (MRE)

OBJECTIVE: Magnetic resonance elastography (MRE) requires substantial data processing based on phase image reconstruction, wave enhancement, and inverse problem solving. The objective of this study is to propose a new, fast MRE method based on MR raw data processing, particularly adapted to applications requiring fast MRE measurement or high elastogram update rate. MATERIALS AND METHODS: The proposed method allows measuring tissue elasticity directly from raw data without prior phase image reconstruction and without phase unwrapping. Experimental feasibility is assessed both in a gelatin phantom and in the liver of a porcine model in vivo. Elastograms are reconstructed with the raw MRE method and compared to those obtained using conventional MRE. In a third experiment, changes in elasticity are monitored in real-time in a gelatin phantom during its solidification by using both conventional MRE and raw MRE. RESULTS: The raw MRE method shows promising results by providing similar elasticity values to the ones obtained with conventional MRE methods while decreasing the number of processing steps and circumventing the delicate step of phase unwrapping. Limitations of the proposed method are the influence of the magnitude on the elastogram and the requirement for a minimum number of phase offsets. CONCLUSION: This study demonstrates the feasibility of directly reconstructing elastograms from raw data

On the characterization of the heterogeneous mechanical response of human brain tissue

The mechanical characterization of brain tissue is a complex task that scientists have tried to accomplish for over 50 years. The results in the literature often differ by orders of magnitude because of the lack of a standard testing protocol. Different testing conditions (including humidity, temperature, strain rate), the methodology adopted, and the variety of the species analysed are all potential sources of discrepancies in the measurements. In this work, we present a rigorous experimental investigation on the mechanical properties of human brain, covering both grey and white matter. The influence of testing conditions is also shown and thoroughly discussed. The material characterization performed is finally adopted to provide inputs to a mathematical formulation suitable for numerical simulations of brain deformation during surgical procedures.</p

Physiologic cardiovascular strain and intrinsic wave imaging

Cardiovascular disease remains the primary killer worldwide. The heart, essentially an electrically driven mechanical pump, alters its mechanical and electrical properties to compensate for loss of normal mechanical and electrical function. The same adjustment also is performed in the vessels, which constantly adapt their properties to accommodate mechanical and geometrical changes related to aging or disease. Real-time, quantitative assessment of cardiac contractility, conduction, and vascular function before the specialist can visually detect it could be feasible. This new physiologic data could open up interactive therapy regimens that are currently not considered. The eventual goal of this technology is to provide a specific method for estimating the position and severity of contraction defects in cardiac infarcts or angina. This would improve care and outcomes as well as detect stiffness changes and overcome the current global measurement limitations in the progression of vascular disease, at little more cost or risk than that of a clinical ultrasound. Copyright © 2011 by Annual Reviews. All rights reserved.link_to_subscribed_fulltex

A 2D FEM for shear wave modeling applied to soft tissues

International audienc

A 2D finite element model for shear wave propagation in biological soft tissues: Application to magnetic resonance elastography

International audienc