Channel Assignment and Access System Selection in Heterogeneous Wireless Network with Unlicensed Bands

Kazuhiko Kinoshita,Kazuki Ginnan,Keita Kawano,Hiroki Nakayama,Tsunemasa Hayashi,Takashi Watanabe 한국통신학회 2020 한국통신학회 APNOMS Vol.2020 No.09

In recent years, LTE system with unlicensed bands is proposed. It can achieve not only to boost the capacity of cellular networks but also to use unlicensed bands effectively since LTE can achieve better spectrum efficiency than Wi-Fi. However, when LTE is introduced into an environment where Wi-Fi access points are already deployed, significant interference may be caused to Wi-Fi. Therefore, the coexistence of LTE and Wi-Fi with unlicensed bands is the problem. In this paper, we assume an environment where LTE base stations and Wi-Fi access points are deployed high-densely with unlicensed bands and co-channel interference frequently is caused. Then, we aim to enhance the average user throughput and its fairness through a centralized control of LTE and Wi-Fi. Specifically, we propose a channel assignment method and a users’ access system selection method using GA. The proposed method enhances both the average user throughput and the fairness of user throughput compared with conventional static channel assignment methods.

Endoscopic Approach via the Minor Papilla for the Treatment of Pancreatic Stones

Takahiro Nakazawa,Kazuki Hayashi,Itaru Naitoh,Fumihiro Okumura,Takashi Joh 대한소화기내시경학회 2012 Clinical Endoscopy Vol.45 No.3

Background/Aims: We aimed to evaluate whether the advanced techniques have influenced the minor papilla approach. Methods: We studied the success rate of guide wire insertion by using ordinary techniques and advanced techniques (rendezvous method and precut method) in 30 patients via the minor papilla. We compared the selection of the access routes between before (52 patients) and after (28 patients) the introduction of the Soehendra stent retriever. Results: In 19 out of 30 patients (63%), guide wire insertion via the minor papilla could be achieved by using ordinary techniques. In total, the guide wire could be inserted in 27 patients (90%) by using the advanced techniques. Before introduction of the Soehendra stent retriever, the major papilla approach was chosen in 38 cases (73%), and the minor papilla approach in 14 cases (27%). After introduction of the Soehendra stent retriever, the major papilla approach was used in 26 cases (93%) and the minor papilla in 2 cases (7%). The frequency of selecting the minor papilla approach has significantly decreased (p<0.05). Conclusions: The advanced techniques have contributed to the improvement of endoscopic approaches via the minor papilla, and decreased the frequency of selecting the minor papilla approach.

Fundamental Study of nanoDot OSL Dosimeters for Entrance Skin Dose Measurement in Diagnostic X-ray Examinations

Okazaki, Tohru,Hayashi, Hiroaki,Takegami, Kazuki,Okino, Hiroki,Kimoto, Natsumi,Maehata, Itsumi,Kobayashi, Ikuo The Korean Association for Radiation Protection 2016 방사선방어학회지 Vol.41 No.3

Background: In order to manage the patient exposure dose in X-ray diagnosis, it is preferred to evaluate the entrance skin dose; although there are some evaluations about entrance skin dose, a small number of report has been published for direct measurement of patient. We think that a small-type optically stimulated luminescence (OSL) dosimeter, named nanoDot, can achieve a direct measurement. For evaluations, the corrections of angular and energy dependences play an important role. In this study, we aimed to evaluate the angular and the energy dependences of nanoDot. Materials and Methods: We used commercially available X-ray diagnostic equipment. For angular dependence measurement, a relative response of every 15 degrees of nanoDot was measured in 40-140 kV X-ray. And for energy dependence measurement, mono-energetic characteristic X-rays were generated using several materials by irradiating the diagnostic X-rays, and the nanoDot was irradiated by the characteristic X-rays. We evaluated the measured response in an energy range of 8.1-75.5 keV. In addition, we performed Monte-Carlo simulation to compare experimental results. Results and Discussion: The experimental results were in good agreement with those of Monte-Carlo simulation. The angular dependence of nanoDot was almost steady with the response of 0 degrees except for 90 and 270 degrees. Furthermore, we found that difference of the response of nanoDot, where the nanoDot was irradiated from the randomly set directions, was estimated to be at most 5%. On the other hand, the response of nanoDot varies with the energy of incident X-rays; slightly increased to 20 keV and gradually decreased to 80 keV. These results are valuable to perform the precise evaluation of entrance skin dose with nanoDot in X-ray diagnosis. Conclusion: The influence of angular dependence and energy dependence in X-ray diagnosis is not so large, and the nanoDot OSL dosimeter is considered to be suitable dosimeter for direct measurement of entrance surface dose of patient.

Which is better for unresectable malignant hilar biliary obstruction: Side-by-side versus stent-in-stent?

Itaru Naitoh,Tadahisa Inoue,Kazuki Hayashi 소화기인터벤션의학회 2018 Gastrointestinal Intervention Vol.7 No.2

Biliary drainage is required for the management of unresectable malignant hilar biliary obstruction (UMHBO), and endoscopic transpapillary drainage is the first-line therapy because it is less invasive. Self-expandable metallic stents (SEMSs) are superior to plastic stents because they have longer stent patency and are more cost-effective. Endoscopic bilateral SEMS placement is technically challenging compared to unilateral placement. However, recent developments in devices and techniques have facilitated bilateral SEMS placement. There are two methods for bilateral hilar SEMS placement for UMHBO: side-by-side (SBS) and stent-in-stent (SIS). Sequential SBS was commonly conducted for bilateral hilar SEMS placement. In a new and thinner delivery system that was developed for SEM placement, two SEMSs could be simultaneously inserted and deployed through the working channel. This new bilateral stenting method enabled us to accomplish simultaneous SBS placement, which increased the success rate of SBS. Insertion of the guidewire and delivery of the second SEMS through the mesh of the first SEMS is challenging in SIS. Newly designed or modified SEMSs that are suitable for SIS have been developed to overcome this challenge, and these SEMSs have facilitated SIS. Uncovered SEMS has been commonly used for hilar SEMS placement, but covered SEMS (CSEMS) is another option for hilar SEMS placement, because CSEMS prevents tumor ingrowth and allows for removal of the stent for re-intervention. Therefore, CSEMS can be used for bilateral SEMS placement in SBS. There are many methods and kinds of SEMS available for bilateral SEMS placement. However, due to lack of evidence, there is no consensus on whether SBS or SIS is optimal for bilateral hilar SEMS placement. In this review, we compared various outcomes between SBS and SIS from previous studies, to clarify which method is better for bilateral SEMS placement for UMHBO.

Which is better for unresectable malignant hilar biliary obstruction: Side-by-side versus stent-in-stent?

Itaru Naitoh,Tadahisa Inoue,Kazuki Hayashi 소화기인터벤션의학회 2018 International journal of gastrointestinal interven Vol.7 No.2

Biliary drainage is required for the management of unresectable malignant hilar biliary obstruction (UMHBO), and endoscopic transpapillary drainage is the first-line therapy because it is less invasive. Self-expandable metallic stents (SEMSs) are superior to plastic stents because they have longer stent patency and are more cost-effective. Endoscopic bilateral SEMS placement is technically challenging compared to unilateral placement. However, recent developments in devices and techniques have facilitated bilateral SEMS placement. There are two methods for bilateral hilar SEMS placement for UMHBO: side-by-side (SBS) and stent-in-stent (SIS). Sequential SBS was commonly conducted for bilateral hilar SEMS placement. In a new and thinner delivery system that was developed for SEM placement, two SEMSs could be simultaneously inserted and deployed through the working channel. This new bilateral stenting method enabled us to accomplish simultaneous SBS placement, which increased the success rate of SBS. Insertion of the guidewire and delivery of the second SEMS through the mesh of the first SEMS is challenging in SIS. Newly designed or modified SEMSs that are suitable for SIS have been developed to overcome this challenge, and these SEMSs have facilitated SIS. Uncovered SEMS has been commonly used for hilar SEMS placement, but covered SEMS (CSEMS) is another option for hilar SEMS placement, because CSEMS prevents tumor ingrowth and allows for removal of the stent for re-intervention. Therefore, CSEMS can be used for bilateral SEMS placement in SBS. There are many methods and kinds of SEMS available for bilateral SEMS placement. However, due to lack of evidence, there is no consensus on whether SBS or SIS is optimal for bilateral hilar SEMS placement. In this review, we compared various outcomes between SBS and SIS from previous studies, to clarify which method is better for bilateral SEMS placement for UMHBO.

Four-Step Classification of Endoscopic Transpapillary Gallbladder Drainage and the Practical Efficacy of Cholangioscopic Assistance

( Michihiro Yoshida ),( Itaru Naitoh ),( Kazuki Hayashi ),( Naruomi Jinno ),( Yasuki Hori ),( Makoto Natsume ),( Akihisa Kato ),( Kenta Kachi ),( Go Asano ),( Naoki Atsuta ),( Hidenori Sahashi ),( Hir 대한소화기학회 2021 Gut and Liver Vol.15 No.3

Background/Aims: Although endoscopic transpapillary gallbladder drainage (ETGBD) has been reported as an alternative procedure for acute cholecystitis, it requires advanced endoscopic techniques. In terms of the certainty of achieving drainage, it remains a challenging procedure. The aim of the current study was to elucidate the practical efficacy of cholangioscopic assistance and to develop a new classification that could be used to evaluate the technical difficulty of ETGBD and provide a theoretical strategy to apply cholangioscopy appropriately for difficult ETGBD. Methods: A total of 101 patients undergoing ETGBD were retrospectively studied. The characteristics and technical outcomes of ETGBD with conventional ETGBD (C-ETGBD) and Spy- Glass DS-assisted ETGBD (SG-ETGBD) were evaluated. The characteristics and technique-dependent factors of unsuccessful C-ETGBD/SG-ETGBD were evaluated using the classification based on the steps of the procedure. The predictive factors of successful C-ETGBD/SG-ETGBD were examined. Results: C-ETGBD was successful in 73 patients (72.3%). SG-ETGBD was successful in 11 of 13 patients (84.6%) who had C-ETGBD failure. Optional SG-ETGBD significantly increased the final success rate (94.1%) compared to C-ETGBD alone (p=0.003). ETGBD procedures could be classified into four steps. SG-assistance worked as an excellent troubleshooter in step 1 (failure to identify the cystic duct orifice) and step 2 (failure of guidewire advancement across the downturned angle of cystic duct takeoff). Magnetic resonance cholangiopancreatography could provide predictive information based on the classification. Conclusions: Optional SG-ETGBD achieved a significantly higher success rate than C-ETGBD alone. Step classification is helpful for determining the technical difficulty of ETGBD and developing a theoretical strategy to apply cholangioscopy in a coordinated manner. (Gut Liver 2021;15:476-485)

Usefulness of Intraductal Ultrasonography in the Diagnosis of Cholangiocarcinoma and IgG4-Related Sclerosing Cholangitis

Takahiro Nakazawa,Itaru Naitoh,Kazuki Hayashi 대한소화기내시경학회 2012 Clinical Endoscopy Vol.45 No.3

The technique of intraductal ultrasonography (IDUS) of the bile duct with a thin-caliber probe and a ropeway system has provided excellent images of the bile duct and periductal structures and is an easy transpapillary approach. In addition, once the guide wire is inserted into the bile duct, IDUS and transpapillary biopsy after endoscopic retrograde cholangiopancreatography can be performed in a single session. Here, we review the usefulness of IDUS in the diagnosis of cholangiocarcinoma and IgG4-related sclerosing cholangitis.

Fundamental Study of nanoDot OSL Dosimeters for Entrance Skin Dose Measurement in Diagnostic X-ray Examinations

Tohru Okazaki,Hiroaki Hayashi,Kazuki Takegami,Hiroki Okino,Natsumi Kimoto,Itsumi Maehata,Ikuo Kobayashi 대한방사선방어학회 2016 방사선방어학회지 Vol.41 No.3

Practical Experiences of Unsuccessful Hemostasis with Covered Self-Expandable Metal Stent Placement for Post-Endoscopic Sphincterotomy Bleeding

Michihiro Yoshida,Tadahisa Inoue,Itaru Naitoh,Kazuki Hayashi,Yasuki Hori,Makoto Natsume,Naoki Atsuta,Hiromi Kataoka 대한소화기내시경학회 2022 Clinical Endoscopy Vol.55 No.1

We reviewed 7 patients with unsuccessful endoscopic hemostasis using covered self-expandable metal stent (CSEMS) placementfor post-endoscopic sphincterotomy (ES) bleeding. ES with a medium incision was performed in 6 and with a large incision in 1patient. All but 1 of them (86%) showed delayed bleeding, warranting second endoscopic therapies followed by CSEMS placement1–5 days after the initial ES. Subsequent CSEMS placement did not achieve complete hemostasis in any of the patients. Lateral-sideincision lines (3 or 9 o’clock) had more frequent bleeding points (71%) than oral-side incision lines (11–12 o’clock; 29%). Additionalendoscopic hemostatic procedures with hemostatic forceps, hypertonic saline epinephrine, or hemoclip achieved excellenthemostasis, resulting in complete hemostasis in all patients. These experiences provide an alert: CSEMS placement is not an ultimatetreatment for post-ES bleeding, despite its effectiveness. The lateral-side of the incision line, as well as the oral-most side, should becarefully examined for bleeding points, even after the CSEMS placement.

Characterization of Elemental Composition and Valence State of Cyclone-collected Aerosol Particles Using EDXRF and XAFS at Three Sites in Japan

Tomoaki Okuda,Weidong Jing,Katsutomo Saito,Takuma Okamoto,Hibiki Saito,Kazuki Sugimoto,Chiharu Nishita-Hara,Keiichiro Hara,Masahiko Hayashi,Shuichi Hasegawa 한국대기환경학회 2022 Asian Journal of Atmospheric Environment (AJAE) Vol.16 No.2

The valence state and concentration of metallic pollutants are important factors contributing to the health effects of respirable particulate matter (PM); however, they have not been well studied. In this study, coarse and fine powder samples of atmospheric PM were collected using a cyclone system at Kanagawa (KO), Saitama (SA), and Fukuoka (FU) in Japan in 2017. Energy dispersive X-ray fluorescence spectroscopy (EDXRF) was used to measure the concentrations of nine metallic elements (Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, and Pb), and X-ray absorption fine structure (XAFS) spectroscopy was used to analyze the valence states of target elements (Cr, Mn, Fe, Cu, and Zn). The EDXRF results indicated that the average contents of Fe, Ti, and Zn were much higher than those of the other six elements in all samples. The XAFS results showed that the major valence states of the elements were Cr(III), Mn(II), Fe(III), Cu(II), and Zn(II). The percentages of Mn(IV), Fe(II), and Cu(0) were higher in KO and SA samples than in FU samples. Mn(0) and Zn(0) were detected in some samples only, and Cu(I) was not detected in any samples. Correlation analysis, principal component analysis, and cluster analysis were performed on the EDXRF and XAFS data of the target elements. The source identification results showed that the sources of metal contaminants in the samples varied considerably between sampling sites and depended on the industrial structure and geographical location of the sampling area. Our findings on the different valence states of the elements may be important for determining the toxicity of PM at different locations.