Computed tomography reconstruction from two transmission measurements for iodine-marked cancer detection

The authors invented the transXend detector, which measures X-rays as electric currents, and then gives the energy distribution of the X-rays after an unfolding process. In a previous paper, it was shown that the material thickness distributions can be estimated with the transXend detector by using reference points plotted from the electric current ratios, such as the I ₂/I ₁ ? I ₃/I ₁ graph, where I_i denotes the electric current measured by the i-th segment of the transXend detector. In this paper, the tomographic images of iodine, aluminum, and the acrylic those surround the other two materials are reconstructed from their material thickness distributions, which are estimated from two X-ray incidence directions. The X-ray event ratios are also used to estimate the material thickness distributions.     

Low-dose exposure energy-resolved X-ray computed tomography using a contrast agent with a high-energy K-edge

X-ray computed tomography (CT) with iodine contrast agent is widely employed to locate cancers. However, this method has shortcomings such as high-radiation dose exposure, iodine side effects, and a beam hardening effect. We have been working on the energy-resolved CT measurement method using a novel X-ray detection system, the “transXend” detector, which measures X-rays as electric currents and gives the energy distribution of incident X-rays after analysis. In the present study, we propose a method for low-dose exposure CT that involves the combination of the energy-resolved CT method, which is free from the beam hardening effect, and a harmless contrast agent with high-energy K-edge absorption, such as gold nanoparticles expected as a future contrast agent. Comparisons of radiation dose exposures as functions of aluminum filter thickness at the exit aperture of an X-ray tube and the K-edge energies of contrast agents are described.     

Performance improvement of the filter-type ‘transXend’ energy-resolving detector by considering noise sensitivity

The filter-type ‘transXend’ detector is an energy-resolving X-ray detector consisting of an energy-integrating flat-panel detector and multiple filters. In our previous studies, we have shown the effectiveness of the transXend detector, but the filters used were not optimized. To obtain better performance, the filters, especially their thickness and material, should be considered. In this paper, we present a method that can preliminarily estimate filter performance by comparing their noise sensitivity before carrying out numerous experiments. Two kinds of filter sets, Cu–Sn and W–Ag, with various thicknesses were evaluated. The results suggest that to image a 20-cm-thick object with 120-kV X-rays, an unfiltered channel and a channel filtered with 0.5-mm-thick Sn or 0.4-mm-thick Ag may be the best combination. The optimal filter thickness will be smaller if the object is thinner and the tube voltage is lower. For applications that require a wide dynamic range of detector response, a channel with a W filter may be better than an unfiltered channel. To verify the calculation results, computed tomography imaging experiments with a 3-cm-diameter phantom were also performed, and the experimental results showed good agreement with the calculation results.     

Experimental studies of optical Raman amplifiers for 1.3‐µm wavelength band and its application to 20 Gbit/s × 2 WDM transmission

Configurations of a Raman amplifier suitable for a 1.3‐µm wavelength band are discussed and their properties are experimentally investigated. Pump light with a wavelength of 1.23 µm that is necessary for the Raman amplification in the 1.3‐µm wavelength band is obtained using a 1.06‐µm fiber laser and Raman laser technique. Concerning the Raman laser, wavelength conversion from 1.06 µm to 1.23 µm is effectively achieved using a cavity configuration including fiber Bragg gratings and a dispersion‐shifted fiber. On the other hand, a conventional dispersion compensation fiber which has an essential property of high nonlinearity is applied in order to obtain large gain at 1.3 µm. Net gain of 35 dB and output power of 15 dBm are achieved. To confirm the applicability of the Raman amplifiers to high‐speed optical transmissions, experiments of 20 Gbit/s × 2 WDM repeaterless transmission through a 80‐km conventional single‐mode fiber are carried out. The 1.3‐µm signal should be degraded due to the dispersion caused by the dispersion compensation fiber in the Raman amplifier; However, bit error rate of less than 10 to 12 is obtained at both wavelengths, which is sufficient performance for practical uses. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(1): 58–65, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10137     

Low-Thermal-Expansion Properties of Sodium- and Lithium-Substituted Cubic Cesium Leucite Compounds

Cubic cesium leucite-based compounds, namely cesium leucites, cesium sodium leucites, and cesium lithium leucites, were synthesized using a multistep solid-state reaction method. The thermal expansion properties, in the temperature range of 298-1273 K, for the synthesized cubic cesium leucite-based compounds were examined using high-temperature powder X-ray diffractometry data. The thermal expansions of the cubic cesium leucite-based compounds were found to vary with the chemical composition. For instance, the thermal expansions of Cs_0.7Na_0.2Al_0.9Si_2.1O₆ and Cs_0.7Li_0.2Al_0.9Si_2.1O₆ were 0.14% at 1273 K and 0.081% at 1073 K, values lower than those of Cs_0.9Al_0.9Si_2.1O₆, which were 0.16% at 1073 K and 0.2% at 1273 K. The results showed that the thermal expansions of the cubic cesium leucite-based compounds changed with ionic substitution at the Cs⁺ sites because of ionic size differences between Cs⁺ and the Na⁺ or Li⁺ substitutional ions.     

Photolysis of poly(3-buten-2-one), poly(4,4-dimethyl-1-penten-3-one), and poly(3-methyl-3-buten-2-one) in the presence of oxygen

Photolysis of poly(3-buten-2-one) (PMVK), poly(4,4-dimethyl-1-penten-3-one) (PBVK), and poly(3-methyl-3-buten-2-one) (PMIK) were carried out in dioxane under oxygen or nitrogen bubbling. The main chain degradations of PBVK and PMIK were quenched and polymeric peroxides were produced. The heat treatment of the polymer irradiated in the presence of oxygen promoted the degradation. The photodegradation of PMVK was enhanced in the presence of oxygen.     

GaAs varactor diode for u.h.f. t.v. tuners

The design and fabrication of a GaAs varactor diode for u.h.f. t.v. tuners were carried out using a GaAs double epitaxial layer. The capacitance ratio of diode. C3/C25, is 6.0 and the series resistance at 470 MHz is 0.24 ?. These characteristics are much better than those of an Si diode and well satisfy the requirements for t.v. tuners.     

Novel screening system for protein-protein interactions by bimolecular fluorescence complementation in Saccharomyces cerevisiae

For high-throughput screening of protein-protein interactions, we have developed a novel yeast screening system using Bimolecular fluorescence complementation (BiFC). Two yeast plasmids, in which genes of heterodimerized peptides LZA and LZB were each fused with those of non-fluorescent half fragments of Kusabira-Green mutant (mKG2), were transformed into a- and α-type yeast, respectively. Mating of them gave a library, which was screened by following green fluorescence resulted from LZA-LZB interaction. The method showed potential ability to detect the positive clones from a model library, in which green-fluorescent and non-fluorescent yeast was mixed in a ratio of 1:675.     

Current steel forgings and their properties for steam generator of nuclear power plant

Current steel forgings used for the construction of steam generators (SGs) for a nuclear power plant (NPP) were introduced from the following three (3) features. (1) Integral type steel forgings such as (i) primary head integrated with nozzles, manways and supports, (ii) steam drum head integrated with nozzle and handhole, (iii) conical shell integrated with cylindrical sections and handholes, have been developed to enhance the structural integrity of the component and to make fabrication and inspection including in-service inspection easier. (2) The high strength steel such as SA508 Cl.3a has been adopted to decrease the weight of components, resulting in enhancement of aseismatic properties of SG. (3) Low Si SA508 Cl.3 steel with the addition of Al was investigated and was applied to a heavy thick tube sheet forging, to minimize the macro- and micro-segregations in the ingot.