Degradable Gelatin Microspheres as an Embolic Agent: an Experimental Study in a Rabbit Renal Model

Shinichi Ohta,Norihisa Nitta,Masashi Takahashi,Kiyoshi Murata,Yasuhiko Tabata 대한영상의학회 2007 Korean Journal of Radiology Vol.8 No.5

Objective: To investigate the basic characteristics of degradable gelatin microspheres (GMSs), including their embolic behavior and degradation periods when they are used as embolic materials in the renal arteries of rabbit models. Materials and Methods: Based on the GMS particle size, 24 kidneys were divided into 3 groups of eight kidneys, and each group was embolized with a different GMS particle size (group 1: 35 100 m, group 2: 100 200 m, and group 3: 200 300 m). From each group, two rabbits were sacrificed immediately after embolization (day 0), and a pair of rabbits from each group underwent an angiogram and were sacrificed on days 3, 7, and 14, respectively, after embolization. The level of arterial occlusion, the pathological changes in the renal parenchyma, and the degradation of the GMSs were evaluated angiographically and histologically. Results: A follow-up angiogram on days 0, 3, 7, and 14 revealed the presence of wedge-shaped poorly-enhanced areas in the parenchymal phase as seen in all groups. The size of these areas tended to increase with the particle diameter, and persisted up to day 14. On days 3, 7, and 14, parenchymal infarctions were observed histologically in all cases, and this observation corresponded with the parenchyma being supplied by the embolized arteries. GMSs of group 1 mainly reached the interlobular arteries, while those of group 3 mainly reached the interlobar arteries. In all but two cases, the GMSs were identified histologically even on day 14, and sequential degradation was histologically identified in all GMS groups. Conclusion: GMSs can be used as degradable embolic materials which can control the level of embolization.

Evaluation of Topology Optimization Objectives in IP Networks

Y. Sinan Hanay,Shinichi Arakawa,Masayuki Murata 한국통신학회 2019 Journal of communications and networks Vol.21 No.4

In the past, various optimization objective functions havebeen proposed to help in network optimization, especially for usein traffic engineering (TE) and topology optimization. This varietyof optimization objectives resulted in the emergence of algorithmstargeting different objectives. However, the role of the objectivefunction has been largely overlooked. Because, the choiceof a particular objective function was not justified in most of thecases. Some researchers criticized this arbitrary selection of objectivefunctions. Even though some researchers intuitively suggestusing a specific objective, only few work tackled with the problemof evaluating the objectives. In this paper, we evaluate various networkoptimization objectives on topology optimization. Previously,a study analyzed the efficiency of some routing optimization objectivesusing linear programming (LP) by linear relaxation. However,some of the objective functions are nonlinear, and such a linear relaxationdoes not treat each objective equally.The difficulty arisesdue to the fact that optimization algorithms are objective functiontailored heuristics. To achieve fairness, we compare and analyzedifferent traffic optimization objectives for topology optimizationusing neural networks which are used to model nonlinear relations. By using neural networks, we strive to avoid any unfairness, suchas obviating linear approximation. Also, our work suggests whichfeatures are meaningful for machine learning in network optimization. Our method partially agrees with the previous work, and weconclude that delay is the best performing optimization objective.

All CMOS Multi-Output Voltage Reference Circuitry unaffected by fluctuation of Ambient Temperature and Supply Voltage

Kentaro Kawabata,Yasoji Suzuki,Shinichi Murata 대한전자공학회 2005 ITC-CSCC :International Technical Conference on Ci Vol.2005 No.1

Techniques for percutaneous transesophageal gastrotubing

Yozo Sato,Shohei Chatani,Takaaki Hasegawa,Shinichi Murata,Yoshitaka Inaba 소화기인터벤션의학회 2021 International journal of gastrointestinal interven Vol.10 No.2

Percutaneous transesophageal gastrotubing (PTEG) procedure was developed in Japan as an alternative access route into the gastrointestinal tract, and it has been performed for patients in whom percutaneous endoscopic gastrostomy would be technically difficult to place or is contraindicated, such as in a prior gastrectomy and massive ascites. In the PTEG procedure, an indwelling tube is inserted through the cervical esophagus, which gives the patient a slight discomfort after the tube placement. Therefore, PTEG is performed not only for enteral feeding, but also for bowel decompression as a palliative care in patients with malignant gastrointestinal obstruction. Recently, several reports of PTEG from countries outside Japan indicated a high technical success rate without major complications. Furthermore, the usefulness of PTEG for bowel decompression as a palliative care was reported in prospective studies. In fact, PTEG is a technically feasible and safe procedure worldwide.

Endoscopic necrosectomy through a self-expandable metallic stent placed percutaneously for walled-off pancreatic necrosis

Yozo Sato,Kazuo Hara,Nozomi Okuno,Shinichi Murata,Takaaki Hasegawa,Hiroyuki Morinaga,Yuki Kimbara,Yugo Imai,Hidekazu Yamaura,Yoshitaka Inaba 소화기인터벤션의학회 2020 International journal of gastrointestinal interven Vol.9 No.3

Walled-off pancreatic necrosis (WOPN) is defined as encapsulated necrotic tissue after severe acute pancreatitis. Treatment strategies for WOPN can be challenging. Although open surgical necrosectomy is the standard treatment for WOPN, it is associated with high rates of morbidity and mortality. Endoscopic necrosectomy, introduced recently, is a treatment option that produces lower rates of morbidity than does open surgery. We report a case of severe WOPN that could not be treated with the usual procedures. Although endoscopic necrosectomy of the left subphrenic and prepancreatic spaces was technically impossible, these spaces could be percutaneously drained. Finally, sufficient drainage of these spaces was achieved with endoscopic necrosectomy through the internal lumen of the self-expandable metallic stent placed percutaneously. This procedure was performed by an endoscopist and an interventional radiologist, and the multidisciplinary approach was useful.

Techniques for percutaneous transesophageal gastrotubing

Yozo Sato,Shohei Chatani,Takaaki Hasegawa,Shinichi Murata,Yoshitaka Inaba 소화기인터벤션의학회 2021 Gastrointestinal Intervention Vol.10 No.2

Percutaneous transesophageal gastrotubing (PTEG) procedure was developed in Japan as an alternative access route into the gastrointestinal tract, and it has been performed for patients in whom percutaneous endoscopic gastrostomy would be technically difficult to place or is contraindicated, such as in a prior gastrectomy and massive ascites. In the PTEG procedure, an indwelling tube is inserted through the cervical esophagus, which gives the patient a slight discomfort after the tube placement. Therefore, PTEG is performed not only for enteral feeding, but also for bowel decompression as a palliative care in patients with malignant gastrointestinal obstruction. Recently, several reports of PTEG from countries outside Japan indicated a high technical success rate without major complications. Furthermore, the usefulness of PTEG for bowel decompression as a palliative care was reported in prospective studies. In fact, PTEG is a technically feasible and safe procedure worldwide.

Endoscopic necrosectomy through a self-expandable metallic stent placed percutaneously for walled-off pancreatic necrosis

Yozo Sato,Kazuo Hara,Nozomi Okuno,Shinichi Murata,Takaaki Hasegawa,Hiroyuki Morinaga,Yuki Kimbara,Yugo Imai,Hidekazu Yamaura,Yoshitaka Inaba 소화기인터벤션의학회 2020 Gastrointestinal Intervention Vol.9 No.3

Walled-off pancreatic necrosis (WOPN) is defined as encapsulated necrotic tissue after severe acute pancreatitis. Treatment strategies for WOPN can be challenging. Although open surgical necrosectomy is the standard treatment for WOPN, it is associated with high rates of morbidity and mortality. Endoscopic necrosectomy, introduced recently, is a treatment option that produces lower rates of morbidity than does open surgery. We report a case of severe WOPN that could not be treated with the usual procedures. Although endoscopic necrosectomy of the left subphrenic and prepancreatic spaces was technically impossible, these spaces could be percutaneously drained. Finally, sufficient drainage of these spaces was achieved with endoscopic necrosectomy through the internal lumen of the self-expandable metallic stent placed percutaneously. This procedure was performed by an endoscopist and an interventional radiologist, and the multidisciplinary approach was useful.

Percutaneous metallic stent placement for malignant afferent loop syndrome via the blind end of the jejunal limb after biliary reconstruction

Yozo Sato,Shohei Chatani,Takaaki Hasegawa,Shinichi Murata,Takamichi Kuwahara,Kazuo Hara,Yasuhiro Shimizu,Yoshitaka Inaba 소화기인터벤션의학회 2021 Gastrointestinal Intervention Vol.10 No.1

Background: Malignant afferent loop syndrome occurs after biliary reconstruction and is difficult to treat because of the complicated anatomical changes. The aim of this study was to investigate the safety and efficacy of percutaneous metallic stent placement for malignant afferent loop syndrome via the blind end of the jejunal limb after biliary reconstruction. Methods: Percutaneous metallic stent placement via the jejunal limb was performed in five male patients (median age, 68 years; range, 51–88 years) with malignant afferent loop syndrome following pancreatoduodenectomy or bile duct resection with reconstruction at our institute from June 2009 to April 2019. Reconstruction was performed using a modified Child’s method or the Roux-en-Y method, and blind end of the jejunal limb was surgically fixed to the abdominal wall. Percutaneous drainage of the afferent loop was performed via the blind end of the jejunal limb. Subsequently, percutaneous metallic stent placement was performed via the same route. Technical success, clinical success, and complications were retrospectively evaluated. Results: Percutaneous metallic stent placement via the blind end of the jejunal limb was successfully achieved in all six procedures. Additional metallic stent placement was performed due to tumor ingrowth in a patient. Drainage catheters were removed from three patients, clamped in one, and could not be removed in one. Clinical success was achieved in four patients (80%) without major complications. Conclusion: Percutaneous metallic stent placement for malignant afferent loop syndrome via the blind end of the jejunal limb after biliary reconstruction could be a safe and effective procedure.

Percutaneous metallic stent placement for malignant afferent loop syndrome via the blind end of the jejunal limb after biliary reconstruction

Yozo Sato,Shohei Chatani,Takaaki Hasegawa,Shinichi Murata,Takamichi Kuwahara,Kazuo Hara,Yasuhiro Shimizu,Yoshitaka Inaba 소화기인터벤션의학회 2021 International journal of gastrointestinal interven Vol.10 No.1

Background: Malignant afferent loop syndrome occurs after biliary reconstruction and is difficult to treat because of the complicated anatomical changes. The aim of this study was to investigate the safety and efficacy of percutaneous metallic stent placement for malignant afferent loop syndrome via the blind end of the jejunal limb after biliary reconstruction. Methods: Percutaneous metallic stent placement via the jejunal limb was performed in five male patients (median age, 68 years; range, 51–88 years) with malignant afferent loop syndrome following pancreatoduodenectomy or bile duct resection with reconstruction at our institute from June 2009 to April 2019. Reconstruction was performed using a modified Child’s method or the Roux-en-Y method, and blind end of the jejunal limb was surgically fixed to the abdominal wall. Percutaneous drainage of the afferent loop was performed via the blind end of the jejunal limb. Subsequently, percutaneous metallic stent placement was performed via the same route. Technical success, clinical success, and complications were retrospectively evaluated. Results: Percutaneous metallic stent placement via the blind end of the jejunal limb was successfully achieved in all six procedures. Additional metallic stent placement was performed due to tumor ingrowth in a patient. Drainage catheters were removed from three patients, clamped in one, and could not be removed in one. Clinical success was achieved in four patients (80%) without major complications. Conclusion: Percutaneous metallic stent placement for malignant afferent loop syndrome via the blind end of the jejunal limb after biliary reconstruction could be a safe and effective procedure.

Stent-graft placement for treatment of massive hemobilia caused by porto-biliary fistula

Masao Takahashi,Yozo Sato,Kazuo Hara,Nozomi Okuno,Ikuo Dejima,Shinichi Murata,Takaaki Hasegawa,Shohei Chatani,Hiroaki Onaya,Yoshitaka Inaba 소화기인터벤션의학회 2019 International journal of gastrointestinal interven Vol.8 No.4

Proton beam therapy is a type of radiation therapy and a promising modality for cancer management because it involves few adverse effects and high therapeutic efficacy. However, there are reports of acute and late complications because of normal tissue damage. Hemobilia, known as bleeding from the biliary tree, is observed in various conditions, and it can also be of iatrogenic origin such as due to percutaneous hepatobiliary interventions. In most cases, it can be managed conservatively without significant hemorrhage. However, in a few cases with massive hemobilia, further intervention is necessary. We report the successful use of a stent-graft in the portal vein to treat massive hemobilia with porto-biliary fistula that was caused by previous proton beam therapy.