Effect of contrast-enhanced ultrasound (CEUS) on liver stiffness measurements obtained by transient and shear-wave elastography.

BACKGROUND: Since liver fibrosis is one of the most accurate predictors of prognosis in hepatopatic patients, its accurate assessment and staging is a major public health issue. Transient elastography (TE) (Fibroscan, Echosens, Paris, France) and shear wave elastography (SWE) represent the gold standard techniques among non-invasive methods to assess liver fibrosis. Contrast-enhanced ultrasound (CEUS) is increasingly used to diagnose the nature of liver lesions and is often performed together with TE and SWE. In this study we evaluated the effect of CEUS on liver stiffness measurements obtained by TE and SWE. METHODS: A retrospective analysis of ultrasound (US) exams performed by an expert operator was carried out. TE and SWE were performed 30 seconds before and after the execution of CEUS. Statistical analysis was carried out using the statistical software R. Kolmogorov-Smirnov analysis was performed to test the normality of continuous variables. The pre- and post-CEUS liver stiffness values were compared using the Wilcoxon's Test. RESULTS: Ninety-six patients were enrolled. While the measurements were comparable when performed with TE, those obtained by SWE decreased by 6% after administration of the contrast agent (P=0.0005). Fibrosis stage deviated between pre- and post-CEUS in 16 (17%) patients with Fibroscan and 22 (23%) patients with SWE. Among the latter, in 9 cases (10%) a deviation from absent-low (F0-F2) to high-fibrosis (F3, F4), or vice versa, occurred. CONCLUSIONS: Our study, the first to assess the effects of CEUS on US elastography, shows that the contrast agent (Sonovue, Bracco Suisse SA, Cadempino, Switzerland) does not significantly affect liver stiffness measurements obtained by TE, whereas the accuracy decreases when performed by SWE.

Modulating proton diffusion and conductivity in metal-organic frameworks by incorporation of accessible free carboxylic acid groups.

Three multi-carboxylic acid functionalised ligands have been designed, synthesised and utilised to prepare the new barium-based MOFs, MFM-510, -511, and -512, which show excellent stability to water-vapour. MFM-510 and MFM-511 show moderate proton conductivities (2.1 × 10-5 and 5.1 × 10-5 S cm-1, respectively) at 99% RH and 298 K, attributed to the lack of free protons or hindered proton diffusion within the framework structures. In contrast, MFM-512, which incorporates a pendant carboxylic acid group directed into the pore of the framework, shows a two orders of magnitude enhancement in proton conductivity (2.9 × 10-3 S cm-1). Quasi-elastic neutron scattering (QENS) suggests that the proton dynamics of MFM-512 are mediated by "free diffusion inside a sphere" confirming that incorporation of free carboxylic acid groups within the pores of MOFs is an efficient albeit synthetically challenging strategy to improve proton conductivity.

Proton Conduction in a Phosphonate-Based Metal-Organic Framework Mediated by Intrinsic "Free Diffusion inside a Sphere".

Understanding the molecular mechanism of proton conduction is crucial for the design of new materials with improved conductivity. Quasi-elastic neutron scattering (QENS) has been used to probe the mechanism of proton diffusion within a new phosphonate-based metal-organic framework (MOF) material, MFM-500(Ni). QENS suggests that the proton conductivity (4.5 × 10(-4) S/cm at 98% relative humidity and 25 °C) of MFM-500(Ni) is mediated by intrinsic "free diffusion inside a sphere", representing the first example of such a mechanism observed in MOFs.