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Search Results: 1 - 10 of 261 matches for " Yuta Shibamoto "
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Contrast Enhancement of Posterior Mediastinal Ganglioneuromas—Correlation between the Level of Enhancement and Histopathological Features  [PDF]
Yoshiyuki Ozawa, Masaki Hara, Maho Kato, Shigeki Shimizu, Yuta Shibamoto
Open Journal of Radiology (OJRad) , 2014, DOI: 10.4236/ojrad.2014.41016
Abstract:

Purpose: Relationship between CT or MR images and histological findings, especially vascularity, has not been adequately evaluated. The purpose of this study was to investigate correlation between contrast enhancement on CT and MRI and histological findings in posterior mediastinal ganglioneuromas. Materials and Methods: Contrast-enhanced (CE) CT (n = 11) and CE MRI (n = 5) of 12 patients with ganglioneuroma were reviewed. The attenuation, signal intensity, and dynamic enhancement pattern of the tumors were evaluated. The vascularity was histologically evaluated by the numbers of vessels. Results: Enhancement on CE-CT was none, mild, moderate, and high enhancement in 5 (45%), 2 (18%), 3 (27%), and 1 (9%) of the 11 lesions, respectively. Dynamic MRI showed mild, moderate and high enhancement in 3 (60%), 1 (20%) and 1 (20%) cases, respectively. The level of contrast enhancement correlated well only with the number of capillary vessels (r = 0.79, P = 0.0037). Conclusion: The posterior mediastinal ganglioneuromas sometimes show insufficient enhancement particularly on CE-CT. The level of enhancement might correlate with the amount of capillary vessels.

Organizing pneumonia after stereotactic ablative radiotherapy of the lung
Murai Taro,Shibamoto Yuta,Nishiyama Takeshi,Baba Fumiya
Radiation Oncology , 2012, DOI: 10.1186/1748-717x-7-123
Abstract: Background Organizing pneumonia (OP), so called bronchiolitis obliterans organizing pneumonia after postoperative irradiation for breast cancer has been often reported. There is little information about OP after other radiation modalities. This cohort study investigated the clinical features and risk factors of OP after stereotactic ablative radiotherapy of the lung (SABR). Methods Patients undergoing SABR between 2004 and 2010 in two institutions were investigated. Blood test and chest computed tomography were performed at intervals of 1 to 3 months after SABR. The criteria for diagnosing OP were: 1) mixture of patchy and ground-glass opacity, 2) general and/or respiratory symptoms lasting for at least 2 weeks, 3) radiographic lesion in the lung volume receiving < 0.5 Gy, and 4) no evidence of a specific cause. Results Among 189 patients (164 with stage I lung cancer and 25 with single lung metastasis) analyzed, nine developed OP. The incidence at 2 years was 5.2% (95% confidence interval; 2.6-9.3%). Dyspnea were observed in all patients. Four had fever. These symptoms and pulmonary infiltration rapidly improved after corticosteroid therapy. Eight patients had presented with symptomatic radiation pneumonitis (RP) around the tumor 2 to 7 months before OP. The prior RP history was strongly associated with OP (hazard ratio 61.7; p = 0.0028) in multivariate analysis. Conclusions This is the first report on OP after SABR. The incidence appeared to be relatively high. The symptoms were sometimes severe, but corticosteroid therapy was effective. When patients after SABR present with unusual pneumonia, OP should be considered as a differential diagnosis, especially in patients with prior symptomatic RP.
Rebleeding after Stent Grafting for the Celiac Artery Bleeding following Extended Pancreaticoduodenectomy
Kengo Ohta,Masashi Shimohira,Takuya Hashizume,Tatsuya Kawai,Masahiro Muto,Junichi Honda,Yuta Shibamoto
Case Reports in Vascular Medicine , 2013, DOI: 10.1155/2013/781698
Abstract: We report a 74-year-old man with rebleeding following stent grafting for the celiac artery bleeding which developed after extended pancreaticoduodenectomy for cancers of the bile duct and stomach. The site of rebleeding seemed to be different from the site of the first bleeding, so it was considered not an endoleak but a new bleeding. It was successfully treated by placement of another stent graft. 1. Introduction Bleeding after pancreaticoduodenectomy is a fatal complication, and endovascular treatment is widely performed. Recently it has been reported that stent grafting is especially an appropriate treatment [1]. Here, we present a rare complication of rebleeding developing 40 days after stent graft placement in the celiac artery. 2. Case Report A 74-year-old man with distal bile duct cancer and gastric cancer underwent extended pancreaticoduodenectomy. Thereafter, leakage of pancreatic juice occurred, for which drainage treatment was performed. At 12 days after surgery, a bleeding from the drainage tube and low blood pressure were observed, so an emergency angiography was performed. A bleeding from the celiac artery was observed on angiography (Figure 1), and a 5?Fr balloon catheter was inflated in the celiac artery for temporary hemostasis, because we needed some time to discuss with surgeons and to prepare a stent graft. Then, a stent graft (Niti-S; Century Medical, Tokyo, Japan) with a diameter of 10?mm and a length of 5?cm was placed at the celiac artery to the common hepatic artery successfully (Figure 2). Resection of the residual stomach, residual pancreas, and spleen was immediately performed following the stent grafting. After that, wound infection and insufficient anastomosis of the esophagus and jejunum were observed; leukocyte count was 5,400/μL and C-reactive protein level was 5.4?mg/mL. So, drainage treatment was performed. At 40 days after this stent grafting and surgery, melena and reduction of blood pressure were observed. Therefore, emergency angiography was performed, which revealed a bleeding from the celiac artery (Figure 3). It seemed to be from a distal site apart from the site of the first bleeding, and it was considered not a leakage but a new bleeding. Under fluoroscopy, it was confirmed that the stent graft was not broken. Temporary balloon hemostasis was performed again. Then, we discussed with our surgeon and decided to perform the stent grafting, because it seemed really difficult to reach the celiac artery under laparotomy due to strong adhesion caused by the previous operation. Thereafter, the stent graft (Niti-S)
Stereotactic body radiotherapy for stage I lung cancer and small lung metastasis: evaluation of an immobilization system for suppression of respiratory tumor movement and preliminary results
Fumiya Baba, Yuta Shibamoto, Natsuo Tomita, Chisa Ikeya-Hashizume, Kyota Oda, Shiho Ayakawa, Hiroyuki Ogino, Chikao Sugie
Radiation Oncology , 2009, DOI: 10.1186/1748-717x-4-15
Abstract: Between 2004 and 2006, 53 consecutive patients were treated for 55 lesions; 42 were stage I non-small cell lung cancer (NSCLC), 10 were metastatic lung cancers, and 3 were local recurrences of NSCLC. Tumor movement was measured with fluoroscopy under breath holding, free breathing on a couch, and free breathing in the BodyFIX system. SpO2 levels were measured with a finger pulseoximeter under each condition. The delivered dose was 44, 48 or 52 Gy, depending on tumor diameter, in 4 fractions over 10 or 11 days.By using the BodyFIX system, respiratory tumor movements were significantly reduced compared with the free-breathing condition in both craniocaudal and lateral directions, although the amplitude of reduction in the craniocaudal direction was 3 mm or more in only 27% of the patients. The average SpO2 did not decrease by using the system. At 3 years, the local control rate was 80% for all lesions. Overall survival was 76%, cause-specific survival was 92%, and local progression-free survival was 76% at 3 years in primary NSCLC patients. Grade 2 radiation pneumonitis developed in 7 patients.Respiratory tumor movement was modestly suppressed by the BodyFIX system, while the SpO2 level did not decrease. It was considered a simple and effective method for SBRT of lung tumors. Preliminary results were encouraging.Stereotactic body radiotherapy (SBRT) is now spreading worldwide as a new treatment modality for stage I non-small cell lung cancer (NSCLC). Following the pioneering work by Uematsu et al. [1,2], promising clinical results with excellent local control and low complication rates have been reported. Clinical outcomes on 257 patients from 14 institutions in Japan were published recently, which showed a 5-year survival rate of 71% in medically operable patients receiving sufficient radiation doses [3]. At present, SBRT is considered a therapeutic option in stage I NSCLC either for inoperable patients or for patients refusing surgery. SBRT for lung cancer is under
Clinical outcomes of stereotactic body radiotherapy for stage I non-small cell lung cancer using different doses depending on tumor size
Fumiya Baba, Yuta Shibamoto, Hiroyuki Ogino, Rumi Murata, Chikao Sugie, Hiromitsu Iwata, Shinya Otsuka, Katsura Kosaki, Aiko Nagai, Taro Murai, Akifumi Miyakawa
Radiation Oncology , 2010, DOI: 10.1186/1748-717x-5-81
Abstract: Between February 2004 and November 2008, 124 patients with stage I NSCLC underwent SBRT. Total doses of 44, 48, and 52 Gy were administered for tumors with a longest diameter of less than 1.5 cm, 1.5-3 cm, and larger than 3 cm, respectively. All doses were given in 4 fractions.For all 124 patients, overall survival was 71%, cause-specific survival was 87%, progression-free survival was 60%, and local control was 80%, at 3 years. The 3-year overall survival was 79% for 85 stage IA patients treated with 48 Gy and 56% for 37 stage IB patients treated with 52 Gy (p = 0.05). At 3 years, cause-specific survival was 91% for the former group and 79% for the latter (p = 0.18), and progression-free survival was 62% versus 54% (p = 0.30). The 3-year local control rate was 81% versus 74% (p = 0.35). The cumulative incidence of grade 2 or 3 radiation pneumonitis was 11% in stage IA patients and 30% in stage IB patients (p = 0.02).There was no difference in local control between stage IA and IB tumors despite the difference in tumor size. The benefit of increasing the SBRT dose for larger tumors should be investigated further.Stereotactic body radiotherapy (SBRT) for lung tumors was introduced in the mid 1990s [1], and it has been performed in many institutions as a new treatment modality for stage I primary lung cancer and oligometastatic lung cancer. Promising clinical results have been reported despite the use of various treatment protocols [2-9]. According to a recently published survey of SBRT in Japan, the treatment techniques and schedules applied for SBRT for lung cancer varied greatly from institution to institution [10]. The most frequently used schedule was 48 Gy in 4 fractions for both stage IA and IB primary lung cancer and metastatic lung cancer.As a result, it was found that the outcomes of stage IB patients were worse than those of stage IA patients at the same dose [3-5], which suggests that SBRT doses should be adjusted according to tumor size. We have performed
Treatment and prognosis of patients with late rectal bleeding after intensity-modulated radiation therapy for prostate cancer
Shinya Takemoto, Yuta Shibamoto, Shiho Ayakawa, Aiko Nagai, Akihiro Hayashi, Hiroyuki Ogino, Fumiya Baba, Takeshi Yanagi, Chikao Sugie, Hiromi Kataoka, Mikio Mimura
Radiation Oncology , 2012, DOI: 10.1186/1748-717x-7-87
Abstract: Between November 2004 and February 2010, 403 patients with prostate cancer were treated with IMRT at 2 institutions. Among these patients, 64 patients who developed late rectal bleeding were evaluated. Forty patients had received IMRT using a linear accelerator and 24 by tomotherapy. Their median age was 72?years. Each patient was assessed clinically and/or endoscopically. Depending on the severity, steroid suppositories or enemas were administered up to twice daily and Argon plasma coagulation (APC) was performed up to 3 times. Response to treatment was evaluated using the Rectal Bleeding Score (RBS), which is the sum of Frequency Score (graded from 1 to 3 by frequency of bleeding) and Amount Score (graded from 1 to 3 by amount of bleeding). Stoppage of bleeding over 3?months was scored as RBS 1.The median follow-up period for treatment of rectal bleeding was 35?months (range, 12–69?months). Grade of bleeding was 1 in 31 patients, 2 in 26, and 3 in 7. Nineteen of 45 patients (42%) observed without treatment showed improvement and bleeding stopped in 17 (38%), although mean RBS did not change significantly. Eighteen of 29 patients (62%) treated with steroid suppositories or enemas showed improvement (mean RBS, from 4.1?±?1.0 to 3.0?±?1.8, p?=?0.003) and bleeding stopped in 9 (31%). One patient treated with steroid enema 0.5-2 times a day for 12?months developed septic shock and died of multiple organ failure. All 12 patients treated with APC showed improvement (mean RBS, 4.7?±?1.2 to 2.3?±?1.4, p?<?0.001) and bleeding stopped in 5 (42%).After adequate periods of observation, steroid suppositories/enemas are expected to be effective. However, short duration of administration with appropriate dosage should be appropriate. Even when patients have no response to pharmacotherapy, APC is effective.
Robust Optimum Design of Thrust Hydrodynamic Bearings for Hard Disk Drives  [PDF]
Hiromu Hashimoto, Yuta Sunami
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.330193
Abstract: This paper describes the robust optimum design which combines the geometrical optimization method proposed by Hashimoto and statistical method. Recently, 2.5″ hard disk drives (HDDs) are widely used for mobile devices such as laptops, video cameras and car navigation systems. In mobile applications, high durability towards external vibrations and shocks are essentials to the bearings of HDD spindle motor. In addition, the bearing characteristics are influenced by manufacturing error because of small size of the bearings of HDD. In this paper, the geometrical optimization is carried out to maximize the bearing stiffness using sequential quadratic programming to improve vibration characteristics. Additionally, the bearing stiffness is analyzed considering dimensional tolerance of the bearing using statistical method. The dimensional tolerance is assumed to distribute according to the Gaussian distribution, and then the bearing stiffness is estimated by combining the expectation and standard deviation. As a result, in the robust optimum design, new groove geometry of bearing can be obtained in which the bearing stiffness is four times higher than the stiffness of conventional spiral groove bearing. Moreover, the bearing has lower variability compared with the result of optimum design neglecting dimensional tolerance.
Electricity Generation System with Piezoelectric Element Using Acoustic Radiation Energy  [PDF]
Hiroyuki Moriyama, Yuta Yamamura
Journal of Power and Energy Engineering (JPEE) , 2018, DOI: 10.4236/jpee.2018.610001
Abstract: In this study, a circular plate that is installing a piezoelectric element at its center is adopted as energy-harvesting system and is subjected to a harmonic point force. Because this system cannot avoid the influence of its acoustic radiation, the influence is considered theoretically using the equation of plate motion taking into account its radiation impedance and is estimated by the electricity generation efficiency, which is derived from the ratio of the electric power in the electricity generation and the mechanical power supplied to the plate. As a result, the efficiency is suppressed by the acoustic radiation from the plate, so that the efficiencies are so different in whether to take into consideration the radiation impedance or not. Because those results are verified by the electricity generation experiment and radiation acoustic energy has a hopeful prospect for improving the performance of this system, mechanical-acoustic coupling is used to make the most of the acoustic energy. Therefore, a cylinder that has the above plates at both ends is also adopted as the electricity generation system and mechanical-acoustic coupling is caused between the plate vibrations and an internal sound field into the cylindrical enclosure by subjecting one side of each plate to a harmonic point force. Then, the effect of coupling is evaluated by comparing with the efficiencies in the electricity generation system of only plate. Specifically, because the radiation impedance increases with the plate thickness, i.e., with the natural frequency of the plate, it is demonstrated that the effect of coupling becomes remarkable with increasing the thickness on the electricity generation efficiency.
Classically conformal B-L extended Standard Model and phenomenology
Orikasa, Yuta
High Energy Physics - Phenomenology , 2013,
Abstract: Bardeen has argued that once the classically conformal invariance and its minimal violation by quantum anomalies are imposed on the SM, it can be free from the quadratic divergences and hence the gauge hierarchy problem. Under the hypothesis, We investigated the minimal B-L extended SM with a flat Higgs potential at the Planck scale. In this model, the B-L symmetry is radiatively broken at TeV scale. We studied phenomenology and detectability of the model at LHC and the ILC.
Critical exponent for the semilinear wave equation with scale invariant damping
Yuta Wakasugi
Mathematics , 2012, DOI: 10.1007/978-3-319-02550-6
Abstract: In this paper we consider the critical exponent problem for the semilinear damped wave equation with time-dependent coefficients. We treat the scale invariant cases. In this case the asymptotic behavior of the solution is very delicate and the size of coefficient plays an essential role. We shall prove that if the power of the nonlinearity is greater than the Fujita exponent, then there exists a unique global solution with small data, provided that the size of the coefficient is sufficiently large. We shall also prove some blow-up results even in the case that the coefficient is sufficiently small.
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