Two-dimensional “transXend” detector for third-generation energy-resolved computed tomography

The “transXend” detector measures X-rays as electric currents and provides the energy distribution of the measured X-rays after analysis. Capabilities of material distinction, effective atomic number measurement, and low-dose exposure computed tomography (CT) with high K-edge contrast agent from the use of the transXend detector in energy-resolved CT have been demonstrated via the first-generation CT measurements. For application of the principle of the transXend detector to the third-generation CT for human subjects in future work, a method for fabrication of a two-dimensional transXend detector is proposed and demonstrated using a commercial two-dimensional detector and two kinds of strip absorbers. The energy-resolved CT is performed by placing a proposed absorber system in front of a two-dimensional detector, which is used for conventional current measurement CT.     

Self‐Degradable Lipid‐Like Materials Based on “Hydrolysis accelerated by the intra‐Particle Enrichment of Reactant (HyPER)” for Messenger RNA Delivery

RNA‐based therapeutics is a promising approach for curing intractable diseases by manipulating various cellular functions. For eliciting RNA (i.e., mRNA and siRNA) functions successfully, the RNA in the extracellular space must be protected and it must be delivered to the cytoplasm. In this study, the development of a self‐degradable lipid‐like material that functions to accelerate the collapse of lipid nanoparticles (LNPs) and the release of RNA into cytoplasm is reported. The self‐degradability is based on a unique reaction “Hydrolysis accelerated by intra‐Particle Enrichment of Reactant (HyPER).” In this reaction, a disulfide bond and a phenyl ester are essential structural components: concentrated hydrophobic thiols that are produced by the cleavage of the disulfide bonds in the LNPs drive an intraparticle nucleophilic attack to the phenyl ester linker, which results in further degradation. An oleic acid‐scaffold lipid‐like material that mounts all of these units (ssPalmO‐Phe) shows superior transfection efficiency to nondegradable or conventional materials. The insertion of the aromatic ring is unexpectedly revealed to contribute to the enhancement of endosomal escape. Since the intracellular trafficking is a sequential process that includes cellular uptake, endosomal escape, the release of mRNA, and translation, the improvement in each process synergistically enhances the gene expression.     

Optical measurement of electric field vector distribution in a liquid insulator using simultaneous three‐direction optical measurement system

We have already reported on reconstructions of the symmetrical and nonsymmetrical electric field vector distribution using the Kerr electrooptic effect and our unique reconstruction method, a modified computed tomography technique. This reconstruction technique gives an electric field map, that is, the strength and the direction of the electric field vector, on any plane. For the reconstruction of one field vector distribution, it was necessary to measure the light intensity twice while changing the optical axis of optical wedges. Moreover, the intensity measurement must be carried out at many points around the electrode system. Therefore, considerable time was required to measure the electric field distribution. We therefore developed a simultaneous three‐direction optical measurement system with three optical systems combined with the two‐beam method. Using the new measurement system, we measured the electric field distribution on planes in a sphere‐to‐sphere electrode system. It took about 0.1 second to measure the light intensity data for the reconstruction. © 2002 Scripta Technica, Electr Eng Jpn, 139(1): 9–15, 2002; DOI 10.1002/eej.1141     

Absorbed dose estimation using LET dependence in glow curve of thermoluminescent phosphor Li3B7O12:Cu in therapeutic carbon beams

A high temperature ratio (HTR) method has been proposed to correct the linear energy transfer (LET) dependence of thermoluminescent (TL) efficiency. To realize the use of the slab-type thermoluminescence detector (TLD) that based on the phosphor Li₃B₇O₁₂:Cu for heavy charged particle beam, the HTR method has been considered. To improve the reproducibility of HTR, the slow heating rate method is introduced in this report and the coefficient variations of HTR decreased from 10%–20% to 8%. The relation between TL-efficiency, HTR, and LET for Li₃B₇O₁₂:Cu was manifested and the TL-efficiency as a function of HTR was derived in an attempt to measure the absorbed dose without LET information. The feasibility of the HTR method in therapeutic carbon beams was evaluated by comparing the dose estimated by Li₃B₇O₁₂:Cu and by an ionization chamber. The accuracy of dose estimation in carbon beams was improved by using the HTR method, but there is room for further improvement. The use of Li₃B₇O₁₂:Cu in heavy charged particle beams can be materialized with further improvement of HTR sensitivity.     

Irradiation facility and physical characteristics of a 18.5 MeV/n alpha beam for cell killing experiments

A simple irradiation facility for biological experiments using a 18.5 MeV/n alpha beam has been developed. This compact irradiation facility provides a sufficiently uniform irradiation field. Physical characteristics of the alpha beam, such as a dose distribution and LET (linear energy transfer), were measured in this field. The results were consistent with theoretically calculated results.     

γ-Ray measurements in boron neutron capture therapy using BeO ceramic thermoluminescence dosimeter

Journal of Materials Science: Materials in Electronics - In boron neutron capture therapy (BNCT), neutrons and γ-rays cause different biological effects, and it is necessary to discriminate...     

An optical projection system with mirrors for laparoscopy

We propose an optical projection system aimed at improving laparoscopic surgery based on three-dimensional (3D) measurement that gives an effective information for robotic-assisted surgery and computer-aided surgery. Laparoscopic surgery, which involves the creation of small ports through the patient’s body for the laparoscope and surgical instruments, such as clamp, is minimally invasive and has generated a growing interest. There are techniques using the stereo laparoscope to obtain depth information. Active sensing when structured light is added to the laparoscope can reconstruct a 3D shape. However, active sensing that requires projection devices for the structured light leads to an increase in size. Large-sized projection and sensing systems affect surgical procedures. The size of the system is also larger than the size of port for the laparoscope. To remove the obstacle for the surgery, it is important to design downsized systems. For active sensing with the structured light, a small-size projection system is required to use a small port for the laparoscope. Therefore, we built the optical projection system toward downsizing the device to stereoscopic vision of the laparoscope using mirrors, and we show a new shape reconstruction method from its active sensing. Our Experimental results demonstrate the effectiveness of this proposed system and method.     

Chemical composition of 14C in airborne release from the Tokai reprocessing plant, Japan

Fuel reprocessing plant is one of the most important sources of anthropogenic (14)C in the environment. A method was developed to determine the amount and chemical composition of airborne (14)C release from the Tokai reprocessing plant, Japan. Effluent monitoring using this method showed most of the (14)C is released in CO(2) form and the ratio of (14)C in hydrocarbons to the total is less than 3%, not depending on the type of fuel reprocessed. This finding would provide improved understanding on dynamical behaviour of (14)C in the environment and assessment of radioecological impact from nuclear fuel cycle.