Flow Characteristics of Pulp Suspension in a 90° Bend

Masaru Sumida,Kentaro Imamura 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.2

This study investigates the flow characteristics of pulp suspensions flowing through a 90° bend, which is used in the production system of an actual papermaking machine, e.g., for transporting the pulp suspensions from its stock reservoir to the header. Experiments were conducted on pulp suspensions with a fiber concentration Cs of 0.3 and 0.6 wt% and a bend with a diameter of 22 mm and a curvature radius ratio of 4.0. Flow visualization and measurements of the distributions of time-averaged fiber concentration Ca and axial velocity U were performed with a light section method and the particle image velocimetry (PIV) method, respectively, at representative bulk velocities and at various longitudinal stations. The influence of the flow rate on the changes of their distributions in the streamwise direction was examined. The flow characteristics of the pulp suspension depend on the flow pattern in the upstream straight tube and are greatly different from those of the single-phase water flow. For a low flow rate, the flocculated pulp fibers move without getting disentangled in the bend and the distribution of Ca shows a shape bias towards the inner wall side. As the flow rate is increased, Ca becomes larger in the outer part of the bend, and it changes into a rather flat distribution in the downstream tangent.

Factors Predicting Difficult Biliary Cannulation during Endoscopic Retrograde Cholangiopancreatography for Common Bile Duct Stones

Hirokazu Saito,Yoshihiro Kadono,Takashi Shono,Kentaro Kamikawa,Atsushi Urata,Jiro Nasu,Haruo Imamura,Ikuo Matsushita,Tatsuyuki Kakuma,Shuji Tada 대한소화기내시경학회 2022 Clinical Endoscopy Vol.55 No.2

Background/Aims: Difficult biliary cannulation is an important risk factor for post-endoscopic retrograde cholangiopancreatography(ERCP) pancreatitis (PEP). Therefore, this study aimed to identify the factors that predict difficult cannulation for common bile ductstones (CBDS) to reduce the risk for PEP. Methods: This multicenter retrospective study included 1,406 consecutive patients with native papillae who underwent ERCP forCBDS. Factors predicting difficult cannulation for CBDS were identified using univariate and multivariate analyses. Results: Univariate analysis showed that six factors significantly predicted difficult cannulation: ERCP performed by non-expertendoscopists, low-volume center, absence of acute cholangitis, normal serum bilirubin, intradiverticular papilla, and type of majorduodenal papilla. Multivariate analysis identified ERCP performed by non-expert endoscopists (odds ratio [OR], 2.5; p<0.001),low-volume center (OR, 1.6; p<0.001), intradiverticular papilla (OR, 1.3; p=0.007), normal serum bilirubin (OR, 1.3; p=0.038), andabsence of acute cholangitis (OR, 1.3; p=0.049) as factors significantly predicting difficult cannulation for CBDS. Conclusions: Initial cannulation by an experienced endoscopist, early rescue cannulation, or early takeover by an experiencedendoscopist should be considered when performing ERCP for CBDS in the presence of factors predicting difficult cannulation.

White Opaque Substance, a New Optical Marker on Magnifying Endoscopy: Usefulness in Diagnosing Colorectal Epithelial Neoplasms

Kazutomo Yamasaki,Takashi Hisabe,Kenshi Yao,Hiroshi Ishihara,Kentaro Imamura,Tatsuhisa Yasaka,Hiroshi Tanabe,Akinori Iwashita,Toshiharu Ueki 대한소화기내시경학회 2021 Clinical Endoscopy Vol.54 No.4

Background/Aims: A white substance that is opaque to endoscopic light is sometimes observed in the epithelium during narrowbandimaging with magnifying endoscopy of gastric or colorectal epithelial neoplasms. This prospective observational study aimedto determine whether the morphology of the white opaque substance (WOS) allows differential diagnosis between colorectaladenoma and carcinoma. Methods: A consecutive series of patients with colorectal adenomas or early carcinomas who underwent endoscopic resectionor surgical excision were studied. The morphology of the WOS was determined based on endoscopic images before thehistopathological diagnosis was performed. The primary outcome was the diagnostic performance of an irregular WOS as a markerof colorectal carcinoma. Results: The study analyzed 125 lesions. A total of 33 lesions showed an irregular WOS, and 92 lesions showed a regular WOS. Among the 33 lesions found to show an irregular WOS, 30 were carcinomas. Among the 92 lesions showing a regular WOS, 79 wereadenomas. With irregular WOS as a marker of carcinoma, the diagnostic accuracy was 87%, sensitivity was 91%, and specificity was86%. Conclusions: This study demonstrated the potential usefulness of the morphology of the WOS as a marker for the differentialdiagnosis between adenoma and carcinoma in cases of colorectal epithelial neoplasms.

Histological Architecture of Gastric Epithelial Neoplasias That Showed Absent Microsurface Patterns, Visualized by Magnifying Endoscopy with Narrow-Band Imaging

Kenta Chuman,Kenshi Yao,Takao Kanemitsu,Takashi Nagahama,Masaki Miyaoka,Haruhiko Takahashi,Kentaro Imamura,Rino Hasegawa,Toshiharu Ueki,Hiroshi Tanabe,Seiji Haraoka,Akinori Iwashita 대한소화기내시경학회 2021 Clinical Endoscopy Vol.54 No.2

Background/Aims: The objective of this study was to elucidate the histological structure of the absent microsurface patterns (MSPs)that were visualized by magnifying endoscopy with narrow-band imaging (M-NBI). Methods: The study included consecutive gastric epithelial neoplasias for which M-NBI findings and histological findings couldbe compared on a one-to-one basis. The lesions were classified as absent MSPs and present MSPs based on the findings obtainedusing M-NBI. Of the histopathological findings for each lesion that corresponded to M-NBI findings, crypt opening densities, cryptlengths, crypt opening diameters, intercrypt distances, and crypt angles were measured and compared. Results: Thirty-six lesions were included in the analysis; of these, 17 lesions exhibited absent MSP and 19 lesions exhibited presentMSP. Comparing the histological measurements for absent MSPs vs. present MSPs, median crypt opening density was 0.9 cryptopenings/mm vs. 4.8 crypt openings/mm (p<0.001), respectively. The median crypt length, median crypt opening diameter, medianintercrypt distance, and median crypt angle were 80.0 μm vs. 160 μm (p<0.001), 40.0 μm vs. 44.2 μm (p=0.09), 572.5 μm vs. 166.7μm (p<0.001), and 21.6 degrees vs. 15.5 degrees (p<0.001), respectively. Conclusions: Histological findings showed that lesions exhibiting absent MSPs had lower crypt opening density, shorter crypt length,greater intercrypt distance, and larger crypt angle.

Efficacy of endoscopy under general anesthesia for the detection of synchronous lesions in oro-hypopharyngeal cancer

Yoichiro Ono,Kenshi Yao,Yasuhiro Takaki,Satoshi Ishikawa,Kentaro Imamura,Akihiro Koga,Kensei Ohtsu,Takao Kanemitsu,Masaki Miyaoka,Takashi Hisabe,Toshiharu Ueki,Atsuko Ota,Hiroshi Tanabe,Seiji Haraoka 대한소화기내시경학회 2023 Clinical Endoscopy Vol.56 No.3

Background/Aims: Image-enhanced endoscopy can detect superficial oro-hypopharyngeal squamous cell carcinoma; however, reliable endoscopy of the pharyngeal region is challenging. Endoscopy under general anesthesia during transoral surgery occasionally reveals multiple synchronous lesions that remained undetected on preoperative endoscopy. Therefore, we aimed to determine the lesion detection capability of endoscopy under general anesthesia for superficial oro-hypopharyngeal squamous cell carcinoma. Methods: This retrospective study included 63 patients who underwent transoral surgery for superficial oropharyngeal squamous cell carcinoma between April 2005 and December 2020. The primary endpoint was to compare the lesion detection capabilities of preoperative endoscopy and endoscopy under general anesthesia. Other endpoints included the comparison of clinicopathological findings between lesions detected using preoperative endoscopy and those newly detected using endoscopy under general anesthesia. Results: Fifty-eight patients (85 lesions) were analyzed. The mean number of lesions per patient detected was 1.17 for preoperative endoscopy and 1.47 for endoscopy under general anesthesia. Endoscopy under general anesthesia helped detect more lesions than preoperative endoscopy did (p<0.001). The lesions that were newly detected on endoscopy under general anesthesia were small and characterized by few changes in color and surface ruggedness. Conclusions: Endoscopy under general anesthesia for superficial squamous cell carcinoma is helpful for detecting multiple synchronous lesions.

Association between occurrence of multiple white and flat elevated gastric lesions and oral proton pump inhibitor intake

Rino Hasegawa,Kenshi Yao,Takao Kanemitsu,Hisatomi Arima,Takayuki Hirase,Yuuya Hiratsuka,Kazuhiro Takeda,Kentaro Imamura,Kensei Ohtsu,Yoichiro Ono,Masaki Miyaoka,Takashi Hisabe,Toshiharu Ueki,Hiroshi T 대한소화기내시경학회 2024 Clinical Endoscopy Vol.57 No.1

Background/Aims: Multiple white and flat elevated lesions (MWFL) that develop from the gastric corpus to the fornix may be strongly associated with oral antacid intake. Therefore, this study aimed to determine the association between the occurrence of MWFL and oral proton pump inhibitor (PPI) intake and clarify the endoscopic and clinicopathological characteristics of MWFL. Methods: The study included 163 patients. The history of oral drug intake was collected, and serum gastrin levels and anti-Helicobacter pylori immunoglobulin G antibody titers were measured. Upper gastrointestinal endoscopy was performed. The primary study endpoint was the association between MWFL and oral PPI intake. Results: In the univariate analyses, MWFL were observed in 35 (49.3%) of 71 patients who received oral PPIs and 10 (10.9%) of 92 patients who did not receive oral PPIs. The occurrence of MWFL was significantly higher among patients who received PPIs than in those who did not (p<0.001). Moreover, the occurrence of MWFL was significantly higher in patients with hypergastrinemia (p=0.005). In the multivariate analyses, oral PPI intake was the only significant independent factor associated with the presence of MWFL (p=0.001; odds ratio, 5.78; 95% confidence interval, 2.06–16.2). Conclusions: Our findings suggest that oral PPI intake is associated with the presence of MWFL (UMINCTR 000030144).