Characterization of spatiotemporal deformation dynamics and material properties requires non-destructive methods to visualize mechanics of materials and biological tissues. Displacement-encoded magnetic resonance imaging (MRI) has emerged as a noninvasive and non-destructive technique used to quantify deformation and strains. However, the techniques are not yet applicable to a broad range of materials and load-bearing tissues. In this paper, we visualize transient and internal material deformation through the novel synchrony of external mechanical loading with rapid displacement-encoded MRI. We achieved deformation measurements in silicone gel materials with a spatial resolution of 100 µm and a temporal resolution (of 2.25 ms), set by the repetition time (TR) of the rapid MRI acquisition. Displacement and strain precisions after smoothing were 11 µm and 0.1%, respectively, approaching cellular length scales. Short (1/2 TR) echo times enabled visualization of in situ deformation in a human tibiofemoral joint, inclusive of multiple variable T₂ biomaterials. Moreover, the MRI acquisitions achieved a fivefold improvement in imaging time over previous technology, setting the stage for mechanical imaging in vivo. Our results provide a general approach for noninvasive and non-destructive measurement, at high spatial and temporal resolution, of the dynamic mechanical response of a broad range of load-bearing materials and biological tissues.

This study demonstrates the in vitro displacement and strain of articular cartilage in a cyclically‐compressed and intact joint using displacement‐encoded imaging with stimulated echoes (DENSE) and fast spin echo (FSE). Deformation and strain fields exhibited complex and heterogeneous patterns. The displacements in the loading direction ranged from −1688 to −1481 μm in the tibial cartilage and from −1601 to −764 μm in the femoral cartilage. Corresponding strains ranged from −9.8% to 0.7% and from −4.3% to 0.0%. The displacement and strain precision were determined to be 65 μm and less than 0.2%, respectively. Displacement‐encoded magnetic resonance imaging is capable of determining the nonuniform displacements and strains in the articular cartilage of an intact joint to a high precision. Knowledge of these nonuniform strains is critical for the in situ characterization of normal and diseased tissue, as well as the comprehensive evaluation of repair constructs designed using regenerative medicine. Magn Reson Med, 2009.