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Search Results: 1 - 10 of 3670 matches for " Yutaka Saito "
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THz-Wave Generation from GaP THz Photonic Crystal Waveguides under Difference-Frequency Mixing  [PDF]
Kyosuke Saito, Tadao Tanabe, Yutaka Oyama
Optics and Photonics Journal (OPJ) , 2012, DOI: 10.4236/opj.2012.223030
Abstract: GaP terahertz (THz) two-dimensional (2D) photonic crystal (PC) waveguides with line defects were fabricated using inductively-coupled plasma reactive-ion etching (ICP-RIE) in Ar/Cl2 gas chemistries. THz-wave generation from the fabricated PC waveguides was demonstrated under collinear phase-matched difference-frequency generation (DFG), using Cr:Forsterite (Cr:F) lasers as the incident source. We compared the THz-wave output characteristics of the PC waveguides with that of GaP planar waveguides. The collinear phase-matching conditions in the DFG process were satisfied for 300- and 500-μm-wide PC waveguide structures at 0.7 and 0.6 THz, respectively. The additional output peaks that appeared near the edge of the photonic band gap, around 0.5 THz, were attributed to the guiding modes in the PC waveguide; no such peaks appeared in the non-patterned ridge waveguides. These experimental results suggest that the phonon-polariton confinement in THz-PC waveguides based on the GaP crystal could be used to enhance the nonlinear optical effect for THz-wave generation.
Narrow-band imaging optical chromocolonoscopy: Advantages and limitations
Fabian Emura, Yutaka Saito, Hiroaki Ikematsu
World Journal of Gastroenterology , 2008,
Abstract: Narrow-band imaging (NBI) is an innovative optical technology that modifies the center wavelength and bandwidth of an endoscope’s light into narrow-band illumination of 415 ± 30 nm. NBI markedly improves capillary pattern contrast and is an in vivo method for visualizing microvessel morphological changes in superficial neoplastic lesions. The scientific basis for NBI is that short wavelength light falls within the hemoglobin absorption band, thereby facilitating clearer visualization of vascular structures. Several studies have reported advantages and limitations of NBI colonoscopy in the colorectum. One difficulty in evaluating results, however, has been non-standardization of NBI systems (Sequential and non-sequential). Utilization of NBI technology has been increasing worldwide, but accurate pit pattern analysis and sufficient skill in magnifying colonoscopy are basic fundamentals required for proficiency in NBI diagnosis of colorectal lesions. Modern optical technology without proper image interpretation wastes resources, confuses untrained endoscopists and delays inter-institutional validation studies. Training in the principles of “optical image-enhanced endoscopy” is needed to close the gap between technological advancements and their clinical usefulness. Currently available evidence indicates that NBI constitutes an effective and reliable alternative to chromocolonoscopy for in vivo visualization of vascular structures, but further study assessing reproducibility and effectiveness in the colorectum is ongoing at various medical centers.
What are the latest developments in colorectal endoscopic submucosal dissection?
Toshio Uraoka,Yutaka Saito,Naohisa Yahagi
World Journal of Gastrointestinal Endoscopy , 2012, DOI: 10.4253/wjge.v4.i7.296
Abstract: Endoscopic submucosal dissection (ESD) enables direct submucosal dissection so that even large early-stage gastrointestinal tumors can be resected en bloc. ESD has recently been applied to the colorectum since it was originally developed for use in the stomach. However, colorectal ESD is technically more difficult with an increased risk of perforation compared with gastric ESD. In addition, this procedure is seldom performed in Western countries. Consequently, further technical advances and the availability of a suitable clinical training system are required for the extensive use of colorectal ESD. In this topic highlight, we review the most recent developments in colorectal ESD.
Improved Measurements of RNA Structure Conservation with Generalized Centroid Estimators
Yutaka Saito,Kengo Sato,Yasubumi Sakakibara
Frontiers in Genetics , 2011, DOI: 10.3389/fgene.2011.00054
Abstract: Identification of non-protein-coding RNAs (ncRNAs) in genomes is a crucial task for not only molecular cell biology but also bioinformatics. Secondary structures of ncRNAs are employed as a key feature of ncRNA analysis since biological functions of ncRNAs are deeply related to their secondary structures. Although the minimum free energy (MFE) structure of an RNA sequence is regarded as the most stable structure, MFE alone could not be an appropriate measure for identifying ncRNAs since the free energy is heavily biased by the nucleotide composition. Therefore, instead of MFE itself, several alternative measures for identifying ncRNAs have been proposed such as the structure conservation index (SCI) and the base pair distance (BPD), both of which employ MFE structures. However, these measurements are unfortunately not suitable for identifying ncRNAs in some cases including the genome-wide search and incur high false discovery rate. In this study, we propose improved measurements based on SCI and BPD, applying generalized centroid estimators to incorporate the robustness against low quality multiple alignments. Our experiments show that our proposed methods achieve higher accuracy than the original SCI and BPD for not only human-curated structural alignments but also low quality alignments produced by CLUSTAL W. Furthermore, the centroid-based SCI on CLUSTAL W alignments is more accurate than or comparable with that of the original SCI on structural alignments generated with RAF, a high quality structural aligner, for which twofold expensive computational time is required on average. We conclude that our methods are more suitable for genome-wide alignments which are of low quality from the point of view on secondary structures than the original SCI and BPD.
Terahertz Wave Generation via Nonlinear Parametric Process from ε-GaSe Single Crystals Grown by Liquid Phase Solution Method  [PDF]
Kyosuke Saito, Yuki Nagai, Kunihiko Yamamoto, Kensaku Maeda, Tadao Tanabe, Yutaka Oyama
Optics and Photonics Journal (OPJ) , 2014, DOI: 10.4236/opj.2014.48021

Terahertz (THz)-wave generation has been conducted based on difference frequency mixing (DFM) process with phonon-polariton excitation of ε-GaSe single crystals implemented with liquid-phase solution growth using the temperature difference method under controlled vapour pressure for the first time. The type-eoo phase matching condition for the DFM process at around 10 THz is satisfied by changing the incident angle into the crystal. The maximum conversion efficiency in the present DFG process is about 10-6 J-1 using a 0.1-mm-thick GaSe single crystal with the only ε- phase polytype, which can be greater than that of the commercially available Bridgman grown GaSe crystal including both ε- and γ-phase polytypes.

New reduced volume preparation regimen in colon capsule endoscopy
Yasuo Kakugawa,Yutaka Saito,Shoichi Saito,Kenji Watanabe
World Journal of Gastroenterology , 2012, DOI: 10.3748/wjg.v18.i17.2092
Abstract: AIM: To evaluate the effectiveness of our proposed bowel preparation method for colon capsule endoscopy. METHODS: A pilot, multicenter, randomized controlled trial compared our proposed “reduced volume method” (group A) with the “conventional volume method” (group B) preparation regimens. Group A did not drink polyethylene glycol electrolyte lavage solution (PEG-ELS) the day before the capsule procedure, while group B drank 2 L. During the procedure day, groups A and B drank 2 L and 1 L of PEG-ELS, respectively, and swallowed the colon capsule (PillCam COLON capsule). Two hours later the first booster of 100 g magnesium citrate mixed with 900 mL water was administered to both groups, and the second booster was administered six hours post capsule ingestion as long as the capsule had not been excreted by that time. Capsule videos were reviewed for grading of cleansing level. RESULTS: Sixty-four subjects were enrolled, with results from 60 analyzed. Groups A and B included 31 and 29 subjects, respectively. Twenty-nine (94%) subjects in group A and 25 (86%) subjects in group B had adequate bowel preparation (ns). Twenty-two (71%) of the 31 subjects in group A excreted the capsule within its battery life compared to 16 (55%) of the 29 subjects in group B (ns). Of the remaining 22 subjects whose capsules were not excreted within the battery life, all of the capsules reached the left side colon before they stopped functioning. A single adverse event was reported in one subject who had mild symptoms of nausea and vomiting one hour after starting to drink PEG-ELS, due to ingesting the PEG-ELS faster than recommended. CONCLUSION: Our proposed reduced volume bowel preparation method for colon capsule without PEG-ELS during the days before the procedure was as effective as the conventional volume method.
Case of a Superficial Hypopharyngeal Cancer at the Pharyngoesophageal Junction Which Is Detected by Transnasal Endoscopy Using Trumpet Maneuver  [PDF]
Kenro Kawada, Tatsuyuki Kawano, Taro Sugimoto, Toshihiro Matsui, Masafumi Okuda, Taichi Ogo, Yuuichiro Kume, Yutaka Nakajima, Katsumasa Saito, Naoto Fujiwara, Tairo Ryotokuji, Yutaka Miyawaki, Yutaka Tokairin, Yasuaki Nakajima, Kagami Nagai, Takashi Ito
Open Journal of Gastroenterology (OJGas) , 2015, DOI: 10.4236/ojgas.2015.51001
Abstract: Aims: In order to observe the pharyngoesophageal junction, the trumpet maneuver with trans-nasal endoscopy was used. Its efficacy is reported here. Material and Methods: A 71-year-old man who underwent esophagectomy in esophageal cancer 2 years ago was admitted to our hospital with primary pharyngeal cancer. The type of upper endoscope used was EG-580NW (FUJI Film, Tokyo, Japan). The endoscope is a trans-nasal endoscope that can provide high quality endoscopic images. The pharyngeal cancer located at right lateral wall which was previously detected could be observed easily. We asked the patient to blow hard and puff his cheeks with his mouth closed. When inspecting the hypopharynx and the orifice of the esophagus, we told the patient that we would start the trumpet maneuver. Results: After the trumpet maneuver, the pharyngeal mucosa was stretched out. Another primary lesion was observed at the posterior wall of the hypopharynx near the pharyngoesophageal junction. This technique provided a much better view of the lesion than had been possible with trans-oral endoscopy,allowing us to remove the biopsy specimen without sedation. Conclusion: In conclusion, the trumpet maneuver using trans-nasal endoscopy is a useful technique for precise inspection before treatments for patients who have already detected the lesions.
Prospective Case Study on Characterization of Colorectal Adenomas Comparing AFI with NBI
Haruhisa Suzuki,Yutaka Saito,Takahisa Matsuda,Takeshi Nakajima,Tsuyoshi Kikuchi
Diagnostic and Therapeutic Endoscopy , 2011, DOI: 10.1155/2011/963618
Abstract: Aim. Compare the characterization ability of AFI and NBI for colorectal adenomas. Methods. We prospectively enrolled 58 patients with 89 colorectal adenomas detected by white light colonoscopy. Such lesions were subsequently observed with both AFI and NBI and then treated by endoscopic resection. With respect to the 89 lesions, 3 experienced endoscopists retrospectively evaluated the visualization quality of the AFI and NBI images in a blind manner using a three-tier scale based on excellent, fair, and poor criteria. Results. There were 54, 31, and 4 lesions considered as excellent, fair, and poor visualization, respectively, using AFI in comparison to 53, 19, and 17 lesions, respectively, with NBI. The percentage of excellent and fair visualization lesions was 95.5% with AFI and 80.9% with NBI ( ). Conclusion. This study indicated that AFI may be more effective for the characterization of colorectal adenomas because of better visualization of such lesions compared to NBI. 1. Introduction Colorectal cancer is the fourth most common form of cancer and the second leading cause of cancer-related deaths in the United States [1]. Current trends suggest that colorectal cancer will soon become a major cause of morbidity and mortality in Japan as well [2] so detection and removal of colorectal adenomas by colonoscopy is becoming an increasingly important means of preventing such cancer [3]. Small or flat adenomas may be missed, however, during conventional colonoscopy examinations [4, 5]. In particular, depressed type colorectal tumors and nongranular type laterally spreading tumors (LST-NGs) have a high potential for malignancy [6, 7] even those smaller in size, but such lesions can be difficult to detect using standard white light colonoscopy (WLC). Although chromoendoscopy provides advantages over conventional colonoscopy in the detection of small lesions, the procedure is more complicated and takes longer [8]. In order to detect colorectal adenomas without the necessity of using chromoendoscopy, therefore, a need exists for the development of a new effective endoscopic method for that specific purpose. The autofluorescence imaging (AFI) [9–12] and narrow-band imaging (NBI) [13–16] videoendoscope systems are recently developed noninvasive optical-digital imaging processes. It has been reported that both systems have an advantage over standard WLC in terms of providing better visualization and, therefore, may be able to improve the endoscopic characterization of colorectal adenomas. There have been no published reports, however, that have actually compared
Progress and Challenges in Colorectal Cancer Screening
Enrique Quintero,Cesare Hassan,Carlo Senore,Yutaka Saito
Gastroenterology Research and Practice , 2012, DOI: 10.1155/2012/846985
Abstract: Although faecal and endoscopic tests appear to be effective in reducing colorectal cancer incidence and mortality, further technological and organizational advances are expected to improve the performance and acceptability of these tests. Several attempts to improve endoscopic technology have been made in order to improve the detection rate of neoplasia, especially in the proximal colon. Based on the latest evidence on the long-term efficacy of screening tests, new strategies including endoscopic and faecal modalities have also been proposed in order to improve participation and the diagnostic yield of programmatic screening. Overall, several factors in terms of both efficacy and costs of screening strategies, including the high cost of biological therapy for advanced colorectal cancer, are likely to affect the cost-effectiveness of CRC screening in the future.
Submucosal injection solution for gastrointestinal tract endoscopic mucosal resection and endoscopic submucosal dissection
Toshio Uraoka, Yutaka Saito, Kazuhide Yamamoto, Takahiro Fujii
Drug Design, Development and Therapy , 2008, DOI: http://dx.doi.org/10.2147/DDDT.S3219
Abstract: bmucosal injection solution for gastrointestinal tract endoscopic mucosal resection and endoscopic submucosal dissection Review (4814) Total Article Views Authors: Toshio Uraoka, Yutaka Saito, Kazuhide Yamamoto, Takahiro Fujii Published Date August 2008 Volume 2008:2 Pages 131 - 138 DOI: http://dx.doi.org/10.2147/DDDT.S3219 Toshio Uraoka1, Yutaka Saito2, Kazuhide Yamamoto1, Takahiro Fujii3 1Department of Gastroenterology and Hepatology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan; 2Division of Endoscopy, National Cancer Center Hospital, Tokyo, Japan; 3TF Clinic, Tokyo, Japan Abstract: Endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) have provided new alternatives for minimally invasive treatment of gastrointestinal adenomas and early-stage cancers that involve a minimum risk of lymph-node metastasis. The use of submucosal injections is essential to the success of these endoscopic resection techniques. The “ideal” submucosal injection solution should provide a sufficiently high submucosal fluid cushion for safe and effective EMRs and ESDs while also preserving lesion tissue for accurate histopathological assessment. In the past, normal saline (NS) solution was commonly used for this purpose, but it is difficult to achieve the proper submucosal elevation and maintain the desired height with NS. Therefore, other safe and effective facilitative submucosal injection solutions have been developed that also take into account relevant cost-benefit considerations. This review examines recent advances in the development of effective submucosal injection solutions for use during endoscopic resections.
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