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Search Results: 1 - 10 of 1297 matches for " Kazuhiro Katada "
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Evaluation of Effective Dose Using the k-Factor of Optimal Scan Range for CT Examination  [PDF]
Masanao Kobayashi, Yasuki Asada, Kosuke Matsubara, Tomonobu Haba, Yuta Matsunaga, Ai Kawaguchi, Kazuhiro Katada, Hiroshi Toyama, Kichiro Koshida, Ryoichi Kato, Shouichi Suzuki
Open Journal of Radiology (OJRad) , 2015, DOI: 10.4236/ojrad.2015.53021
Abstract: The American College of Radiology opened the computed tomography (CT) dose index registry (DIR) for general participation by all facilities in 2011. For each CT examination, data on volume CT dose index (CTDIvol), dose-length product (DLP), and, for body examinations, size-specific dose estimate (SSDE) were collected. However, effective dose is not estimated in DIR. The primary objective of this study was to estimate k-factor profile in detail at various scan positions with modified the ImPACT CT patient dosimetry. A tool that easily estimates the k-factor of suitable scan areas is essential for practical dose estimation in the DIR. We evaluated k-factor (effective dose/ DLP) profiles between a medical international radiation dose-five (MIRD-5) phantom positions using aImPACT software. As a result of this study, practicality of the k-factor profile method in clinical use was clarified. We speculate that a flexible k-factor improves the appropriateness of the E in hospital settings.
Effect of Edge-Preserving Adaptive Image Filter on Low-Contrast Detectability in CT Systems: Application of ROC Analysis
Miwa Okumura,Takamasa Ota,Kazuhisa Kainuma,James W. Sayre,Michael McNitt-Gray,Kazuhiro Katada
International Journal of Biomedical Imaging , 2008, DOI: 10.1155/2008/379486
Abstract: Objective. For the multislice CT (MSCT) systems with a larger number of detector rows, it is essential to employ dose-reduction techniques. As reported in previous studies, edge-preserving adaptive image filters, which selectively eliminate only the noise elements that are increased when the radiation dose is reduced without affecting the sharpness of images, have been developed. In the present study, we employed receiver operating characteristic (ROC) analysis to assess the effects of the quantum denoising system (QDS), which is an edge-preserving adaptive filter that we have developed, on low-contrast resolution, and to evaluate to what degree the radiation dose can be reduced while maintaining acceptable low-contrast resolution. Materials and Methods. The low-contrast phantoms (Catphan 412) were scanned at various tube current settings, and ROC analysis was then performed for the groups of images obtained with/without the use of QDS at each tube current to determine whether or not a target could be identified. The tube current settings for which the area under the ROC curve (Az value) was approximately 0.7 were determined for both groups of images with/without the use of QDS. Then, the radiation dose reduction ratio when QDS was used was calculated by converting the determined tube current to the radiation dose. Results. The use of the QDS edge-preserving adaptive image filter allowed the radiation dose to be reduced by up to 38%. Conclusion. The QDS was found to be useful for reducing the radiation dose without affecting the low-contrast resolution in MSCT studies.
Prediction and Treatment of Difficult Cases in Colorectal Endoscopic Submucosal Dissection
Yutaka Inada,Naohisa Yoshida,Munehiro Kugai,Kazuhiro Kamada,Kazuhiro Katada,Kazuhiko Uchiyama,Osamu Handa,Tomohisa Takagi,Hideyuki Konishi,Nobuaki Yagi,Yuji Naito,Naoki Wakabayashi,Akio Yanagisawa,Yoshito Itoh
Gastroenterology Research and Practice , 2013, DOI: 10.1155/2013/523084
Abstract: Purpose. The aim of this study was to examine the characteristics of difficult cases and the learning curve in colorectal endoscopic submucosal dissection (ESD). Methods. We studied 518 colorectal tumors treated by ESD. Patients were divided into 2 groups such as the difficult ESD group and non-difficult ESD group in view of procedure time and procedure speed, respectively. The clinical features in each group were analyzed, and we also examined cases with severe fibrosis. Furthermore, we divided all cases into 5 periods according to experience of ESDs and investigated the rates of difficult and perforation cases. Results. In view of both procedure time and procedure speed, there were significant differences about mean tumor size, rates of severe fibrosis and perforation, and en bloc resection rate between the two groups. Severe fibrosis was detected in protruding tumors >40?mm in diameter. With respect to the learning curve, the rate of difficult and perforation cases decreased significantly in the late periods compared to the first period. Conclusions. Large tumor size, high rates of severe fibrosis and perforation, and low rate of en bloc resection are related with difficult ESD cases. The increasing of experiences can decrease the rate of difficult cases and perforation. 1. Introduction In Japan and some other Western and Asian countries, ESD is reported to be an efficient treatment with a high rate of en bloc resection for large colorectal tumors, and ESD is less invasive than laparoscopic colectomy (LAC) [1]. ESD should be performed for tumors that are diagnosed as intramucosal cancer and shallowly invaded submucosal cancer [2, 3]. The number of colorectal ESD has increased gradually with the development of safer strategies and improvements of suitable ESD devices. However, the control of endoscopes and ESD knives are hindered in some colorectal ESD cases because the colon is winding and has many folds. Additionally, restlessness resulting from abdominal fullness and pain is related to prolonged procedure times [4, 5]. It is therefore important to predict difficult cases to prevent complications, including perforation [5, 6]. In this study, we investigated difficult ESD cases with long procedure times or slow procedure speed and examined learning curve of ESD. 2. Patients and Methods A total of 518 tumors in 418 patients who underwent ESD at the Kyoto Prefectural University of Medicine or Nara City Hospital from 2006 to 2013 were analyzed. We examined clinical outcomes for all 518 tumors and divided the tumors into 2 groups such as the difficult
Phase I Clinical Trial of Fibronectin CH296-Stimulated T Cell Therapy in Patients with Advanced Cancer
Takeshi Ishikawa, Satoshi Kokura, Tatsuji Enoki, Naoyuki Sakamoto, Tetsuya Okayama, Mitsuko Ideno, Junichi Mineno, Kazuko Uno, Naohisa Yoshida, Kazuhiro Kamada, Kazuhiro Katada, Kazuhiko Uchiyama, Osamu Handa, Tomohisa Takagi, Hideyuki Konishi, Nobuaki Yagi, Yuji Naito, Yoshito Itoh, Toshikazu Yoshikawa
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0083786
Abstract: Background Previous studies have demonstrated that less-differentiated T cells are ideal for adoptive T cell transfer therapy (ACT) and that fibronectin CH296 (FN-CH296) together with anti-CD3 resulted in cultured cells that contain higher amounts of less-differentiated T cells. In this phase I clinical trial, we build on these prior results by assessing the safety and efficacy of FN-CH296 stimulated T cell therapy in patients with advanced cancer. Methods Patients underwent fibronectin CH296-stimulated T cell therapy up to six times every two weeks and the safety and antitumor activity of the ACT were assessed. In order to determine immune function, whole blood cytokine levels and the number of peripheral regulatory T cells were analyzed prior to ACT and during the follow up. Results Transferred cells contained numerous less-differentiated T cells greatly represented by CD27+CD45RA+ or CD28+CD45RA+ cell, which accounted for approximately 65% and 70% of the total, respectively. No ACT related severe or unexpected toxicities were observed. The response rate among patients was 22.2% and the disease control rate was 66.7%. Conclusions The results obtained in this phase I trial, indicate that FN-CH296 stimulated T cell therapy was very well tolerated with a level of efficacy that is quite promising. We also surmise that expanding T cell using CH296 is a method that can be applied to other T- cell-based therapies. Trial Registration UMIN UMIN000001835
New Genetic Biomarkers Predicting Azathioprine Blood Concentrations in Combination Therapy with 5-Aminosalicylic Acid
Kazuhiko Uchiyama, Tomohisa Takagi, Yasunori Iwamoto, Norihiko Kondo, Tetsuya Okayama, Naohisa Yoshida, Kazuhiro Kamada, Kazuhiro Katada, Osamu Handa, Takeshi Ishikawa, Hiroaki Yasuda, Junichi Sakagami, Hideyuki Konishi, Nobuaki Yagi, Yuji Naito, Yoshito Itoh
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0095080
Abstract: Background and Aims Azathioprine (AZA) is widely used for the treatment of inflammatory bowel disease (IBD) patients. AZA is catabolized by thiopurine S-methyltransferase (TPMT), which exhibits genetic polymorphisms. It has also been reported that 5-aminosalicylic acid (5-ASA) inhibits TPMT activity, and that increased 6-thioguanine nucleotide (6-TGN, a metabolite of AZA) blood concentrations result in an increased number of ADRs. In this study, single nucleotide polymorphisms (SNPs) related to differential gene expression affecting AZA drug metabolism in combination therapy with 5-ASA were examined. Methods To identify genetic biomarkers for the prediction of 6-TGN blood concentration, ExpressGenotyping analysis was used. ExpressGenotyping analysis is able to detect critical pharmacogenetic SNPs by analyzing drug-induced expression allelic imbalance (EAI) of premature RNA in HapMap lymphocytes. We collected blood samples on 38 patients with inflammatory bowel disease treated with AZA and corroboration of the obtained SNPs was attempted in clinical samples. Results A large number of SNPs with AZA/5-ASA-induced EAI within the investigated HapMap lymphocytes was identified by ExpressGenotyping analysis. The respective SNPs were analyzed in IBD patients' blood samples. Among these SNPs, several that have not yet been described to be induced by AZA/5-ASA were found. SNPs within SLC38A9 showed a particular correlation with patients' 6-TGN blood concentrations. Conclusions Based on these results, ExpressGenotyping analysis and genotyping of patients appears to be a useful way to identify inter-individual differences in drug responses and ADRs to AZA/5-ASA. This study provides helpful information on genetic biomarkers for optimized AZA/5-ASA treatment of IBD patients.
Inventories and Mixed Duopoly with State-Owned and Labor-Managed Firms  [PDF]
Kazuhiro Ohnishi
iBusiness (IB) , 2010, DOI: 10.4236/ib.2010.22014
Abstract: This paper considers a two-period mixed market model in which a state-owned firm and a labor-managed firm are allowed to hold inventories as a strategic device. The paper then shows that the equilibrium in the second period occurs at the Stackelberg point where the state-owned firm is the leader.
Price-Setting Mixed Duopoly Models with Complementary Goods  [PDF]
Kazuhiro Ohnishi
Modern Economy (ME) , 2010, DOI: 10.4236/me.2010.11003
Abstract: This paper considers domestic (resp. international) Bertrand mixed duopoly competition in which a state-owned welfare-maximizing public firm and a domestic (resp. foreign) profit-maximizing private firm produce complementary goods. The main purpose of the paper is to present and to compare the equilibrium outcomes of the two mixed duopoly models.
Partial Privatization in Price-Setting Mixed Duopolies with Complementary Goods  [PDF]
Kazuhiro Ohnishi
Modern Economy (ME) , 2011, DOI: 10.4236/me.2011.21007
Abstract: We consider a domestic (resp. international) mixed duopoly model in which a domestic public firm and a domestic (resp. foreign) private firm produce complementary goods. First, the domestic government chooses the level of privatization to maximize domestic social welfare. Second, observing the level of privatization, the firms simultaneously and independently choose prices. We present the equilibrium outcomes of the two mixed duopoly models and shows that our result is in marked contrast to that of the price-setting mixed du-opoly model with substitute goods.
Labor Investment in a New International Mixed Market  [PDF]
Kazuhiro Ohnishi
Technology and Investment (TI) , 2010, DOI: 10.4236/ti.2010.12017
Abstract: This paper considers a continuous-time dynamic mixed market model of labor investment decisions of a domestic public firm and a foreign private firm. The paper studies the optimal levels of preemptive investment for the long-run structure of the international mixed market. It is then demonstrated that there are no perfect equilibria in which neither firm invests to its steady-state reaction curve.
Trochanteric Fracture of a Congenital/Developmental Dislocation of the Hip in an Elderly Woman: A Case Report  [PDF]
Kazuhiro Imai
Open Journal of Orthopedics (OJO) , 2011, DOI: 10.4236/ojo.2011.11001
Abstract: An 87-year-old woman with a residual dislocated hip suffered a trochanteric fracture on the ipsilateral side. The fracture was treated by open reduction and internal fixation surgery with good results. To treat a proximal femoral fracture of the residual dislocated hip in an elderly patient, the patient’s overall status, pre-fracture ability, hip joint configuration, and fracture pattern should be considered.
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