A Comparison of the Prospective Acquisition Correction Technique with Respiratory Triggering Technique in a 3-D MR Pancreaticobiliary System Angiography: A Focus on Normal Healthy Subjects

This study aimed at comparing the quality of images produced using the prospective acquisition correction (PACE) technique based on a navigator with that produced by the respiratory triggering (RT) technique based on a wireless respiratory triggering cushion. Twenty normal healthy people underwent magnetic resonance (MR) cholangiopancreatography based on a three-dimensional (3-D) respiratory triggering technique using either the PACE or RT techniques. For quantitative analysis, the signal-to-noise and contrast-to-noise ratios were calculated. For qualitative analysis, the morphology of the anatomical structures, artifacts due to respiration and the definition of cholangiopancreatography were evaluated based on the following five-point scale. The excellence of the images was also evaluated independently by two specialists in abdominal imaging and two radiological technicians, whose results were analyzed statistically using a Wilcoxon signed-rank test. With regard to the morphology of the anatomical structures and sharpness of the pancreaticobiliary tract, the PACE technique had higher scores than the RT one (P?=?0.07). However, there were no significant differences in artifacts due to respiration between the two techniques (P?=?0.774). The signal-to-noise and contrast-to-noise ratios were significantly higher in the PACE technique (P?<?0.05), with the exception of the common hepatic duct (P?=?0.085). A comparison was made between the PACE and RT techniques in respiratory triggering 3-D MR cholangiopancreatography, which showed that the PACE technique produces a higher image quality.     

Comparison of 2-D Breath-Holding Half-Fourier Acquisition Single-Shot Turbo Spin-Echo Technique with Contrast Agents and 3-D Respiratory-Triggered Fast-Recovery Fast Spin-Echo Technique in MR Cholangiopancreatography

This study compares the quality of technical images in rendering the biliary tree magnetic resonance imaging (MRI) scans based on a three-dimensional (3-D) respiratory-triggered, fast-recovery, rapid spin-echo (3-D RT-FRFSE) technique with that of a 2-D contrast-enhanced breath-holding half-Fourier acquisition single-shot turbo spin-echo (2-D CE-BH-HASTE) technique. The MRI equipment used in this study was a 1.5 T unit (General Electric medical system, excite HD). A total of 30 patients (15 males and 15 females, mean age of 45 years) were examined. A 2-D CE-BH-HASTE technique was used to perform the scan using an interleaved acquisition at a small thickness within 15 s after injecting the contrast medium. The 3-D RT-FRFSE technique is referred to as a respiratory-triggered technique, where the scan is performed in a respiratory-triggered setting so that patients and MRI equipment can synchronize with the respiration. On quantitative analysis, the signal-to-noise ratio was obtained using the biliary tree and background noise, and the absolute contrast-to-noise ratio was obtained using the difference between the biliary tree and its adjacent tissue. On qualitative analysis, two radiologists and three experienced radiological technicians made an assessment based on the anatomic delineation, visibility of eight biliary trees and degree of image artifacts. The difference in image quality between the two techniques was assessed using a paired t-test and Wilcoxon signed-rank test. After quantitative analysis, the signal-to-noise and contrast-to-noise ratios for the common bile duct, common hepatic duct, intrahepatic bile duct, bile duct and pancreatic duct were found to be higher with the 3-D RT-FRFSE technique than with the 2-D CE-BH-HASTE technique. However, the excellent degree of the 3-D RT-FRFSE technique for the common bile duct, bile duct and pancreatic duct solely was significant (p < 0.05). The common hepatic duct showed an equivalent profile in the two techniques (p = 0.041). In addition, the 2-D CE-BH-HASTE technique showed a significant difference for the intrahepatic duct (p < 0.05). On qualitative analysis, the 3-D RT-FRFSE technique produced significant results with the delineation of eight biliary trees as well as anatomical delineation (p = 0.014, 0.039). However, there were no significant results regarding the artifacts of the images (p = 0.808). In conclusion, from the aspects of the quality of technical images, the 3-D RT-FRFSE technique can render the overall shape of biliary tree using a single test compared with the 2-D CE-BH-HASTE technique. However, the concomitant use of the two techniques would be useful for obtaining optimal information on the biliary tree.     

A flexible metamaterial with negative refractive index at visible wavelength

In this paper, we demonstrated a realization of a flexible metamaterial with negative refractive index operating at visible wavelength. With the help of Finite-Difference Time-Domain (FDTD) method, we could establish design rules for the metamaterial and analyze the characteristics of it. To this end, the fishnet structure with the unit cell size 185 nm by 240 nm was fabricated. Due to the polymer dielectric spacer between the metal-layers, the metamaterial is freestanding without base substrate and additional backside etching process.     

Correlation between Hepatic Fat Content Using 3-Echo 3-D Dixon Method and Intravoxel Incoherent Motion (IVIM) Perfusion MR Imaging

Fat accumulates as droplets in the hepatocyte swelling, distortion of microcirculatory anatomy and compression of sinus. This study aims to investigate the correlation between the T2*-corrected fat fraction (FF) value acquired via gradient echo with a low flip angle and parenchymal pseudorandom blood perfusion (P _fraction), microcirculation (D _fast), and slow component of diffusion (D _slow), acquired via intravoxel incoherent motion (IVIM), and to investigate the blood microcirculation and diffusion components of liver parenchyma, according to fat deposition. A total of 126 patients underwent 3-T magnetic resonance imaging, including a 3-echo three-dimensional (3-D) gradient echo sequence with T2*-corrected Dixon reconstruction and IVIM sequence. Pearson’s correlation analysis was conducted to investigate the correlation of the FF obtained via the Dixon method with the apparent diffusion coefficient (ADC), D _slow, P _fraction, and D _fast obtained via IVIM. Correlation analysis was also conducted for the IVIM mapping images. A confidence level of p < 0.05 was set. A negative correlation was found between the T2*-corrected FF acquired using the 3-echo 3-D Dixon method and D _slow acquired via IVIM (r = ?0.181, p < 0.05). It was likely due to the increased extracellular collagen deposition and increased intracellular fat droplets during the progression of liver fibrosis.     

Environmentally friendly electroless plating for Ag/TiO2-coated core–shell magnetic particles using ultrasonic treatment

In this work, high-reflectance brilliant white color magnetic microspheres comprising a Fe/TiO₂/Ag core–shell structure with a continuous, uniform compact silver layer were successfully fabricated by TiO₂-assisted electroless plating in a simple and eco-friendly method. The coating procedure for TiO₂ and Ag involved a sol–gel reaction and electroless plating with ultrasound treatment. The electroless plating step was carried out in an eco-friendly manner in a single process without environmentally toxic additives. The TiO₂ layer was used as a modification layer between the Fe microspheres and the silver layer to improve adhesion. A continuous and compact silver layer could be formed with a high degree of morphological control by introducing ultrasonication and adjusting the ammonium hydroxide concentration.     

A Method for Predicting the Parameters of Plastic Deformation of Dispersedly Reinforced Materials by Using a Modified Mori–Tanaka Model

Mechanics of Composite Materials - A modified Mori–Tanaka model to predict the average mechanical characteristics for dispersedly reinforced materials considering the physical nonlinearity,...     

Finite Sums of Toeplitz Products on the Polydisk

On the Bergman space of the unit polydisk, we study a class of operators which contains sums of finitely many Toeplitz products with pluriharmonic symbols. We give characterizations of when an operator in that class has finite rank or is compact. As one of applications we show that sums of a certain number, depending on and increasing with the dimension, of semicommutators of Toeplitz operators with pluriharmonic symbols cannot be compact without being the zero operator.     

Uncertainty Quantification of Stochastic Simulation for Black-box Computer Experiments

Stochastic simulations applied to black-box computer experiments are becoming more widely used to evaluate the reliability of systems. Yet, the reliability evaluation or computer experiments involving many replications of simulations can take significant computational resources as simulators become more realistic. To speed up, importance sampling coupled with near-optimal sampling allocation for these experiments is recently proposed to efficiently estimate the probability associated with the stochastic system output. In this study, we establish the central limit theorem for the probability estimator from such procedure and construct an asymptotically valid confidence interval to quantify estimation uncertainty. We apply the proposed approach to a numerical example and present a case study for evaluating the structural reliability of a wind turbine.