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Dynamic X-ray elastography using propagating shear waves is a novel technique to visualize the spatial distribution of elasticity in soft materials. We demonstrate that it can be applied to a gel sample with a fine structure. We prepared a viscoelastic gel sample with a two-dimensional lattice structure filled with ZrO2 particles, and applied the technique to map storage and loss moduli. The obtained storage modulus map successfully distinguished the harder lattice structure from the soft gel matrix with a spatial resolution much higher than those of other conventional elastography techniques using magnetic resonance and ultrasound.

This study aimed to develop a refined actuator suitable for psoas major muscle (PM) MR elastography (MRE) and evaluate its measurement precision. MRE was performed on nine healthy volunteers. Discomfort under PM-MRE examinations was evaluated by discomfort scores using a four-point subjective scale. The performance of refined actuator was evaluated in detail; repeatability was evaluated using repeatability coefficients (%RC) according to the Quantitative Imaging Biomarker Alliance (QIBA) and reproducibility with different operators was evaluated using interclass correlation coefficients (ICC). The discomfort score was 1.4 ± 0.53 and it indicated refined actuator was sufficiently comfortable (no pain). In the repeatability study (n = 9), the %RC was approximately 19%, which was comparable to the limit required for clinical liver MREs by the QIBA (19%). In the reproducibility study, the ICCs were > 0.90 (n = 3), indicating that the refined actuator had almost perfect reproducibility. The refined actuator was suitable for PM-MREs and had acceptable repeatability and reproducibility. Refined actuator was expected to meet the standard set by the QIBA (for liver MRE).

Objective Quantitative MR imaging techniques of degenerative cartilage have been reported as useful indicators of degenerative changes in cartilage extracellular matrix, which consists of proteoglycans, collagen, non-collagenous proteins, and water. Apparent diffusion coefficient (ADC) mapping of cartilage has been shown to correlate mainly with the water content of the cartilage. As the water content of the cartilage in turn correlates with its viscoelasticity, which directly affects the mechanical strength of articular cartilage, ADC can serve as a potentially useful indicator of the mechanical strength of cartilage. The aim of this study was to investigate the correlation between ADC and viscoelasticity as measured by indentation testing. Materials and methods Fresh porcine knee joints (n = 20, age 6 months) were obtained from a local abattoir. ADC of porcine knee cartilage was measured using a 3-Tesla MRI. Indentation testing was performed on an electromechanical precision-controlled system, and viscosity coefficient and relaxation time were measured as additional indicators of the viscoelasticity of cartilage. The relationship between ADC and viscosity coefficient as well as that between ADC and relaxation time were assessed. Results ADC was correlated with relaxation time and viscosity coefficient (R2 = 0.75 and 0.69, respectively, p