Quantitative evaluation of simultaneous spatial and temporal regularization in liver perfusion studies using low-dose dynamic contrast-enhanced CT

The purpose of this study was to quantitatively evaluate the performance of different simultaneous spatial and temporal regularizers in liver perfusion studies using low-dose dynamic contrast-enhanced computed tomography (DCE-CT). A digital liver phantom was used to simulate chronic liver disease (CLD) and hepatocellular carcinoma (HCC) based on clinical data. Low-dose DCE-CT images were reconstructed using regularizers and a primal-dual algorithm. Subsequently, hepatic perfusion parameter (HPP) images were generated using a dual-input single-compartment model and linear least-squares method. In the CLD model, the effect of regularizers on the input functions (IFs) was examined by calculating the areas under the curves (AUCs) of the IFs, and the HPP estimation accuracy was evaluated by calculating the error and coefficient of variation (CV) between the HPP values obtained by the above methods and true values. In the HCC model, the ratios of the mean HPP values inside and outside the tumor were calculated. The AUCs of IFs decreased with increasing regularization parameter (RP) values. Although the AUC of arterial IF did not significantly depend on the regularizers, that of portal IF did. The error and CV were reduced using low-rank and sparse decomposition (LRSD). Total generalized variation (TGV) combined with LRSD (LTGV) was generally superior to the other regularizers in terms of HPP estimation accuracy and range of available RP values in both the CLD and HCC models. However, striped artifacts were more remarkable in the HPP images obtained by the TGV and LTGV than in those obtained by the other regularizers. The results suggest that the LRSD and LTGV are useful for improving the accuracy of HPP estimation using low-dose DCE-CT and for enhancing its practicality. This study will help select a suitable regularizer and/or RP value for low-dose DCE-CT liver perfusion studies.Comment: 32 pages, 1 table, 10 figure

Ammonium·18-crown-6 bis(trifluoromethylsulfonyl)amide

We report synthesis and characterization of an ammonium-based molten salt, ammonium bis(trifluoromethylsulfonyl)amide-18-crown-6 (1/1), i.e. [NH₄⁺･18C6][Tf₂N⁻] (Tf = SO₂CF₃). Raman spectra shows [NH₄⁺･18C6][Tf₂N⁻] consists of NH₄⁺ ion encapsulated by 18C6 and Tf₂N⁻ anion. The melting point of [NH₄⁺･18C6][Tf₂N⁻] was around 100°C. At 140°C, the viscosity of [NH₄⁺･18C6][Tf₂N⁻] was 14.7 mPa s, the conductivity was 8.0 mS cm⁻¹, and the density was 1.23 g cm⁻³. These properties were comparable to those of common ionic liquids

Basal-Plane Orientation of Zn Electrodeposits Induced by Loss of Free Water in Concentrated Aqueous Solutions

Concentrated aqueous solutions attract considerable attention because water electrolysis can be suppressed due to a decrease in the amount of free water. The present study focuses on electrodeposition behaviors of metallic zinc (Zn) using concentrated aqueous solutions containing bis(trifluoromethylsulfonyl)amide (Tf₂N⁻) anions. An increase in Tf₂N⁻ concentration significantly enhances water-anion interactions, giving characteristic infrared spectra for the breakdown of the hydrogen-bonding networks of water clusters, i.e. loss of free water. For the Tf₂N⁻ system Zn electrodeposits with the preferred orientation of hcp basal plane was observed, while, for the SO₄²⁻ system with the presence of the hydrogen-bonding networks, preferred orientation of basal plane was not observed. The preferred orientation of basal plane is not attributed to the adsorption of Tf₂N⁻ anions on the electrode, proved by the use of mixed Zn(Tf₂N)₂-ZnSO₄ concentrated solutions. The loss of free water in the concentrated Zn(Tf₂N)₂ solutions will suppress hydrogen adsorption at the cathode to promote surface diffusion of intermediate Zn⁺ adions and growth of Zn crystals. Consequently, the promotions and the easier growth of Zn basal planes with the lowest interfacial free energy will enhance the horizontal growth of Zn basal planes

High-density and low-roughness anodic oxide formed on SiC in highly concentrated LiCl aqueous solution

The wide bandgap and high carrier mobility of silicon carbide (SiC), as well as its physical and chemical stability, make it a promising material for a number of applications. One of the key requirements for these applications involves oxide formation on SiC. The usefulness of the oxide produced by anodizing is, however, limited since the anodic oxide formed on SiC in the usual dilute aqueous solution has a low density and high surface roughness. Here, we consider a new parameter in anodic oxide formation by focusing on the concentration of free water in the electrolyte, using a highly concentrated aqueous solution. In a concentrated solution, oxygen evolution, which results in a reduction in the density of the oxide, is suppressed, and the rate of formation of anodic oxide at defect sites effectively decreases to reduce the surface roughness. Furthermore, an interfacial layer with a higher density than SiO₂ is formed between SiC and SiO₂, buffering the difference in density between them. As a result, we successfully obtained an anodic oxide with a relatively high density and low surface roughness. This study provides a new approach to improving the properties of the anodic oxide formed on SiC

Thermodynamic Design of Electrolyte for CuO/Cu₂O Bilayer by Anodic Electrodeposition

Electrodeposition of multilayered semiconductors requires a bath design to electrodeposit the upper layer(s) without dissolving the base layer(s) below. We present herein a reliable approach to bath design based on thermodynamics from the viewpoint of complexation with ligands. A CuO/Cu₂O bilayer film was targeted as an example. We searched a thermodynamic database of complexation constants for ligands that could form a complex with Cu(II) but not with Cu(I), and identified monoethanolamine as one of the best candidates. Using a Cu(II)-monoethanolamine alkaline aqueous bath, we experimentally confirmed that a CuO upper layer could be deposited without dissolving the Cu₂O base layer. We believe that this design is applicable to other bilayer films produced by electrochemical techniques