MAGNIFYING RATIO and RESOLUTION OF ELECTRONIC ENDOSCOPES

Olympus has been continuing to improve the resolution of its endoscope with each generation developed, and recently it commercialized highly practical magnifying endoscopes such as GIF‐Q24 0Z and CF‐Q240Z. However, the magnifying ratio and resolution of an endoscope are not defined officially by academic conferences. In addition, there is no united definition agreed among endoscope manufacturers. This document aims to explain the definitions of magnifying ratio, maximum magnifying ratio, resolution, and maximum resolution of electronic endoscopes, based on the definitions used by Olympus.     

Development of magnifying video endoscopes with high resolution

Background: The diagnostic capability of a video‐endoscope has been remarkably enhanced by using a high pixel count charge‐coupled device (CCD) and is getting closer to that of the stereomicroscope as its image quality is improved. From this standpoint, the authors have been developing high‐resolution magnifying video‐endoscopes. Methods: There are two methods available to increase the resolution of a video‐endoscope: (i) use a CCD with large pixel number and (ii) optically magnify the image impinging on the CCD. Since the video‐endoscope using a 410 Kilo (K) pixel count CCD was introduced in 1993, the authors have been developing a video‐endoscope using a large pixel count number CCD in pursuit of obtaining better image quality and resolution. Also, the technological innovations in CCD manufacturing have allowed CCDs to become much smaller in size with higher pixel numbers. As the CCD size decreases, the distal part of a video‐endoscope can be made thinner. With respect to optical magnification, two methods are available, the fixed close‐focusing system and variable focus. Results: With combined use of the variable focus magnification and the electronic magnification, a magnification more than × 100 can be achieved on a 14″ television monitor with higher resolution power and wider depth of field. Conclusions: The images captured by the latest magnifying video‐endoscope prove that the image quality of video‐endoscopy is improving and is approaching the diagnostic capability of the stereomicroscope.     

What can we see with the endoscope? Present status and future perspectives

The present status and future perspectives in new technologies of image processing and analysis, infrared ray endoscopy and autofluorescence endoscopy for gastrointestinal cancer are presented in this paper. Spectroscopic measurements using an endoscopic spectroscopic system are useful for distinguishing between benign and malignant gastric mucosal lesions, and the histological classification of early gastric cancer is possible on the basis of the spectroscopic characteristics. It is expected that adaptive hemoglobin index color enhancement would be useful for the qualitative diagnosis of early gastric cancer and for detecting specialized columnar epithelium in Barrett’s esophagus in combination with magnifying endoscopy. Our preliminary experience suggess that magnifying endoscopy with a narrow‐band imaging system could predict the histological characteristics of gastric cancerous lesions with high accuracy. Recent studies revealed that infrared ray electronic endoscopy is very useful for diagnosing the depth of invasion in early gastric cancer. In addition, it is evident that specific antibodies tagged with the indocyanine green derivative can label cancer cells and can generate a fluorescent signal strong enough to detect small cancers using an infrared fluorescence endoscope. The future development and evaluation of autofluorescence endoscopy are discussed, and we propose a modification to the system, including the excitation lights.     

Chromo- and magnifying endoscopy for colorectal lesions

It is essential to identify patients with premalignant or early malignant changes during colonoscopy. Thus, curative resection can be offered. At present, endoscopy can be performed with new powerful high-resolution or magnifying endoscopes. Comparably to the rapid development in chip technology, the optic features of the newly designed endoscopes offer resolutions which allow new mucosal surface details to be seen. In conjunction with chromoendoscopy, the newly discovered tool video endoscopy is much easier and more impressive than with conventional fibre optics. This review summarizes the value of magnifying endoscopy in the lower gastrointestinal tract and focuses on colorectal lesions.     

Magnifying chromoendoscopy for the detection of premalignant gastrointestinal lesions

The prognosis for patients with malignancies of the gastrointestinal tract is strictly dependent on the early detection of premalignant and malignant lesions. At present, endoscopy can be performed with new, powerful high-resolution or magnifying endoscopes. Comparable to the rapid development in chip technology, the optic features of the newly designed endoscopes offer resolutions that allow new mucosal surface details to be seen. In conjunction with chromoendoscopy, the newly discovered tool of video endoscopy is much easier to use and more impressive than previously used fibreoptic endoscopy. This review summarises the value of magnifying endoscopy in the upper and lower gastrointestinal tract and focuses on gastroesophageal reflux disease and early gastric and colorectal cancer.     

Usefulness of magnifying endoscopic evaluation of the terminal ileum for a patient with graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

The gastrointestinal tract is one of the common targets of acute graft-versus-host disease (GVHD), but accurate diagnosis is difficult because of the nonspecific nature of complicated diseases and the lack of diagnostic findings by conventional endoscopy. Recently, a magnifying endoscope has been developed and used for examining microstructures of the mucosa. Herein, we report the first use of a magnifying endoscope for a patient with gastrointestinal (GI) GVHD. Magnified endoscopic findings of atrophic and coalescent villi of the terminal ileum reflect histological findings of GVHD. Magnifying endoscopy of the terminal ileum may be useful for early detection and follow-up of GI GVHD.     

Reprocessing of flexible endoscopes: Scientific rationales and patient safety implications

Proper reprocessing of flexible endoscopes in gastroenterology practice is a critical element of a comprehensive patient safety and infection control strategy in both the inpatient and outpatient healthcare setting. This effort requires an interprofessional approach consisting of collaboration between the endoscopist and multiple other facility stakeholders including reprocessing professionals, nursing, infection prevention and control, biomedical engineering, and patient safety professionals. Recent advancements in human factors engineering has demonstrated a high reliability in validated and standardized reprocessing efforts for flexible endoscopes with properly trained reprocessing personnel and appropriate resources to execute the overall reprocessing process. A continued and concerted effort must be paid to maintaining the safety of these devices through focus on personnel, processes, and a continued innovative engineering of the devices themselves. While flexible endoscopes play a pivotal role in delivering diagnostic and therapeutic medical capabilities to endoscopists, their use is not without risk and require a comprehensive approach to medical device hygiene and integrated infection prevention and control.     

Recent advances in diagnostic upper endoscopy

BACKGROUND Esophageo-gastro-duodenoscopy(EGD)is an important procedure used for detection and diagnosis of esophago-gastric lesions.There exists no consensus on the technique of examination.AIM To identify recent advances in diagnostic EGDs to improve diagnostic yield.METHODS We queried the PubMed database for relevant articles published between January 2001 and August 2019 as well as hand searched references from recently published endoscopy guidelines.Keywords used included free text and MeSH terms addressing quality indicators and technological innovations in EGDs.Factors affecting diagnostic yield and EGD quality were identified and divided into the follow segments:Pre endoscopy preparation,sedation,examination schema,examination time,routine biopsy,image enhanced endoscopy and future developments.RESULTS We identified 120 relevant abstracts of which we utilized 67 of these studies in our review.Adequate pre-endoscopy preparation with simethicone and pronase increases gastric visibility.Proper sedation,especially with propofol,increases patient satisfaction after procedure and may improve detection of superficial gastrointestinal lesions.There is a movement towards mandatory picture documentation during EGD as well as dedicating sufficient time for examination improves diagnostic yield.The use of image enhanced endoscopy and magnifying endoscopy improves detection of squamous cell carcinoma and gastric neoplasm.The magnifying endoscopy simple diagnostic algorithm is useful for diagnosis of early gastric cancer.CONCLUSION There is a steady momentum in the past decade towards improving diagnostic yield,quality and reporting in EGDs.Other interesting innovations,such as Raman spectroscopy,endocytoscopy and artificial intelligence may have widespread endoscopic applications in the near future.     

Video endoscopy

The advent of the video endoscope is the most profound change in the design of gastrointestinal endoscopes since the introduction of the optical fibre bundle. As a television system, it is more expensive than existing systems but surpasses them in quality in my opinion. However, the CCD endoscope will not survive only as a special system for television. Although all the currently available and prototype instruments are acceptable for most aspects of diagnostic endoscopy, there is debate as to whether or not the CCD endoscope will replace the fibrescope. I think that this is a distinct possibility, but in order for the video endoscope to supplant the fibrescope it must not only equal it in all respects but must also surpass it in some significant way. This potential superiority hinges on the inherent versatility of the method by which the video endoscope obtains an endoscopic image. This leads readily to any number of methods of electronic and computerized storage, recall, comparison and transmission of endoscopic data, capabilities that can be used to advantage in many areas. In research that utilizes endoscopic methods it will prove invaluable; properly interfaced with other technological developments it can greatly increase the efficiency of an endoscopy unit. Remarkable as these possibilities may be, however, it is the prospect of computerized and electronic manipulation of the endoscopic images that most threatens the position of the fibrescope. If emerging CCD technology provides useful methods of diagnosis that go beyond simple observation in the visible light spectrum, then the argument will be decided in favour of the video endoscope. What form this will take, and when it will come to pass, remain to be seen.     

USEFULNESS OF MAGNIFYING ENDOSCOPY IN UPPER GASTROINTESTINAL TRACT: HISTORY AND RECENT STUDIES

Although clinical trials using magnifying optical endoscopy have been reported, magnifying endoscopies have been remarkably developed in the period of electronic endoscopy. Magnifying electronic endoscopies with 80 or 100‐fold magnification are used for routine endoscopic examination of upper gastrointestinal tract in Japan. Magnifying endoscopy is used to visualize the microstructure and microvascular architecture of gastrointestinal surface mucosa. Microsurface structure of the mucosa includes normal structure, changed structure by inflammation and biological response, and tumor‐specific structure. Microvascular architecture includes normal vascular system and tumor microvessels. Magnifying endoscopy is starting to play an important role in diagnosis of any upper gastrointestinal diseases by assessment of magnified observation. Magnifying endoscopy holds a great deal of promise in the near future because magnifying endoscopic observation is approaching optical biopsy.     

ENDOCYTOSCOPIC OBSERVATION OF ESOPHAGEAL SQUAMOUS CELL CARCINOMA

The endocytoscopy system (ECS), adapted for clinical use in 2003, is an ultra‐high‐power magnifying endoscope that allows observations at the cell level. ECS is based on the technology of light‐contact microscopy. The most evident use of ECS is for real‐time, high‐resolution diagnosis of nuclear abnormalities, mainly in patients with esophageal cancer. Up to now, three different types of ECS have been available. This diagnostic tool makes it possible to omit histological examination of biopsy samples in approximately 84% of esophageal squamous cell carcinoma, as evidence for both an increase of cell density and nuclear abnormalities is considered to be convincing proof that a lesion is malignant. Here we describe the features of ECS and the background that led to its development, and review the published literature pertaining to the observation of esophageal neoplasms using ECS.     

Reprocessing of flexible endoscopes and endoscopic accessories - an international comparison of guidelines

Endoscopic examinations and procedures are essential for diagnosis and treatment of gastrointestinal diseases. As a result of poor reprocessing practice microorganisms can be transmitted via endoscope. The majority of infection transmissions is due to insufficient performance of cleaning and disinfection disregarding guidelines of societies of gastrointestinal endoscopy. A review of the literature and a comparison of European and American guidelines for reprocessing flexible endoscopes are given. Differences in the classification of endoscopic devices, on the possibility of prion transmission, recommendations on staff training and protection, quality assurance of reprocessing and evidence-based graduation of guidelines are stressed and discussed. With respect to the procedure of endoscope reprocessing, differences concerning the cleaning solution to choose, necessity of thoroughly manual cleaning and brushing of the accessible endoscope channels (even in the case of subsequent automatic reprocessing endoscopes in washers-disinfectors), disinfection solution, microbiological quality of water for final rinsing and rationale for alcohol flush of endoscope channels for better drying are mentioned. The need for experimental investigations of the cleaning and disinfection process is stressed. In contrast to recent guidelines of European and American societies of gastrointestinal endoscopy, the now updated recommendations of the Robert Koch-Institute for reprocessing flexible endoscopes and endoscopic accessories are evidence-based and graduated.     

ENDOSCOPE CONTAMINATION FROM HBV‐ AND HCV‐POSITIVE PATIENTS AND EVALUATION OF A CLEANING/DISINFECTING METHOD USING STRONGLY ACIDIC ELECTROLYZED WATER

Background: It is well known that strongly acidic electrolyzed water (SAEW) has a potent bactericidal effect. We examined residual viruses on endoscopes that were used in hepatitis B virus (HBV)‐positive and hepatitis C virus (HCV)‐positive patients and evaluated the effectiveness of SAEW in cleaning/disinfecting the endoscopes. Methods: A random sample of endoscopes used in 109 endoscopies on HBV‐positive patients and 107 endoscopies on HCV‐positive patients, who underwent upper gastrointestinal endoscopy for various reasons was taken to determine the degree of HBV and HCV contamination. Samples were taken using 10 mL of physiological saline injected through the forceps channel of each endoscope and collected at the distal end to be assayed using polymerase chain reaction (PCR). After examination, each endoscope was treated with air aspiration, then 200 mL of tap water that contained an enzyme detergent was absorbed, and SAEW was aspirated after cleaning with a brush. After each procedure, PCR was used for comparison and to identify any residual viruses. Results: In saline collected after air aspiration, viruses were detected in 39/109 endoscopes used in HBV patients and in 20/107 endoscopes used in HCV patients. In the saline aspirated with tap water containing an enzyme detergent, HBV was detected in 12/109 endoscopes and HCV was detected in 6/107 endoscopes. However, neither HBV nor HCV was detected after the endoscopes were cleaned manually with a brush and disinfected with SAEW. Conclusion: Endoscopes contaminated with HBV and HCV are effectively cleaned and disinfected by SAEW.     

ANGIOGENESIS IN SUPERFICIAL ESOPHAGEAL SQUAMOUS CELL CARCINOMA: MAGNIFYING ENDOSCOPIC OBSERVATION AND MOLECULAR ANALYSIS

Observations of esophageal squamous cell carcinoma using magnifying endoscopy have now been carried out extensively and, as a result, it has become clear that the morphology of the microvessels evident at the tumor surface reflects the depth of tumor invasion. In M1 and M2 cancer, the surface microvasculature reveals dilation and elongation of the intrapapillary capillary loops (IPCL). However, at this stage, some immature capillaries resembling IPCL also arise inside the tumor and, therefore, the view of the microvasculature should be described as one showing ‘intermixing of modified IPCL and IPCL‐like immature capillaries (IPCL‐like abnormal capillary)’. As cancer invades into the muscularis mucosa (M3 or deeper), an obviously dilated and irregularly branched tumor‐specific vasculature, more accurately described as ‘neovasculature’, can be observed. From our magnifying endoscopy observations and studies of the molecular profile of early esophageal cancer, we conclude that two major angiogenic steps exist in precancerous and M3 lesions in the early phase of cancer progression. In addition, it is now possible to study cell morphology using an endocytoscope with a much higher magnification (×400–×1000) than magnifying endoscopes currently on the market. The histology revealed in this way may reduce the need for conventional biopsy histology in the future.     

Optical performance of electronic imaging systems for the colon

Electronic (video) endoscopes are a significant new development in gastroenterology, offering the potential of enhanced teaching and permanent storage of pictorial data. The primary concern of gastroenterologists is the resolution and color performance of these instruments, as these parameters have important bearings on the ability to discern pathological changes in mucosa. We sought to determine the resolution and color capabilities of electronic colonoscopes and compare them with a conventional fiber colonoscope. Resolution was determined using a standard test chart at various distances and the number of picture elements (a measure of resolution) was calculated. The mean number of picture elements was Fujinon (219), Fiber (172), Pentax (169), Toshiba (142), Olympus (140), and Welch Allyn (133). In close focus examination (target distances less than 1 cm), the Fujinon and Toshiba endoscopes had significantly higher resolution than the other instruments. Color was measured quantitatively using a standard color chart and a color analyzer. Color polygons were plotted for each endoscope on a reference chromaticity diagram. All systems had an acceptable overall performance but color was undersaturated with some systems. The optical performance of electronic endoscopes has improved considerably since the inception of electronic endoscopy.     

Infectious complications in gastrointestinal endoscopy and their prevention

Gastrointestinal endoscopes are medical devices that have been associated with outbreaks of health care-associated infections. Because of the severity and limited treatment options of infections caused by multidrug-resistant Enterobacteriaceae and Pseudomonas aeruginosa, considerable attention has been paid to detection and prevention of these post-endoscopic outbreaks. Endoscope reprocessing involves cleaning, high-level disinfection/sterilization followed by rinsing and drying before storage. Failure of the decontamination process implies the risk of settlement of biofilm producing species in endoscope channels. This review covers the infectious complications in gastrointestinal endoscopy and their prevention and highlights the problem of infection risk associated with different steps of endoscope reprocessing.     

Chromoendoscopy and magnifying endoscopy in patients with gastroesophageal reflux disease. Useful or negligible?

Gastroesophageal reflux disease (GERD) is common in the Western world. Upper endoscopy is needed to characterize the disease. Barrett's esophagus as a complication of GERD is an established precancerous condition which can lead to adenocarcinoma in the distal esophagus. This review summarizes recent advances in the endoscopic characterization of Barrett's esophagus using magnification endoscopy and chromoendoscopy. Methylene blue, indigo carmine and acetic acid are commonly used dyes to facilitate diagnosis of Barrett's esophagus. Methylene blue is absorbed in the specialized columnar epithelium, which is pathognomonic for Barrett's esophagus. Indigo carmine and acetic acid are used as contrast stains to highlight the surface architecture. Currently, different dyes are used in conjunction with magnifying endoscopes to characterize specific surface patterns of Barrett's epithelium. However, the current proposed classifications are too complex relative to their clinical value. Nevertheless, simplification of these systems will occur over time with increased use of magnifying chromoendoscopy. The value of magnifying chromoendoscopy for clinical practice is not determined yet and currently under investigation. However, these techniques have significant potential to improve diagnostic accuracy in patients with Barrett's esophagus.     

Application of artificial intelligence-driven endoscopic screening and diagnosis of gastric cancer

The landscape of gastrointestinal endoscopy continues to evolve as new technologies and techniques become available. The advent of image-enhanced and magnifying endoscopies has highlighted the step toward perfecting endoscopic screening and diagnosis of gastric lesions. Simultaneously, with the development of convolutional neural network, artificial intelligence (AI) has made unprecedented breakthroughs in medical imaging, including the ongoing trials of computer-aided detection of colorectal polyps and gastrointestinal bleeding. In the past demi-decade, applications of AI systems in gastric cancer have also emerged. With AI’s efficient computational power and learning capacities, endoscopists can improve their diagnostic accuracies and avoid the missing or mischaracterization of gastric neoplastic changes. So far, several AI systems that incorporated both traditional and novel endoscopy technologies have been developed for various purposes, with most systems achieving an accuracy of more than 80%. However, their feasibility, effectiveness, and safety in clinical practice remain to be seen as there have been no clinical trials yet. Nonetheless, AI-assisted endoscopies shed light on more accurate and sensitive ways for early detection, treatment guidance and prognosis prediction of gastric lesions. This review summarizes the current status of various AI applications in gastric cancer and pinpoints directions for future research and clinical practice implementation from a clinical perspective.     

Magnifying endoscopy simple diagnostic algorithm for early gastric cancer (MESDA‐G)

Gastric cancer is the third leading cause of cancer death worldwide. Early detection and accurate diagnosis of mucosal cancer is desirable in order to achieve decreased mortality; cause‐specific survival of patients with early gastric cancer is reported to exceed 95%. Endoscopy is the functional modality to detect early cancer; however, the procedure is not definitive when using conventional white‐light imaging. In contrast, magnifying narrow‐band imaging (M‐NBI), a novel endoscopic technology, is a powerful tool for characterizing gastric mucosal lesions because it can visualize the microvascular architecture and microsurface structure. To date, many reports on the diagnosis of early gastric cancer by M‐NBI, including multicenter prospective randomized studies conducted in Japan, have been published in peer‐reviewed international journals. Based on these published data, we devised a proposal for a diagnostic strategy for gastric mucosal cancer using M‐NBI to simplify the process of diagnosis and improve accuracy. Herein, we recommend a diagnostic algorithm for early gastric cancer using magnifying endoscopy.     

Is it proper to use non‐magnified narrow‐band imaging for esophageal neoplasia screening? Japanese single‐center,prospective study

Aim: Most screening examinations in Japanese general hospitals are carried out by high‐definition television‐incompatible (non‐HD) scopes and non‐magnifying endoscopes. We evaluated the narrow‐band imaging (NBI) real‐time diagnostic yield of esophageal neoplasia in high‐risk patients at a general hospital. Methods: In a single‐center, prospective, non‐randomized controlled trial, 117 consecutive screening patients with high risk for esophageal cancer received primary white‐light imaging (WLI) followed by NBI and iodine‐staining endoscopy (59 by HDTV‐compatible [HD] endoscopy and 58 by non‐HD endoscopy). The primary aim was to evaluate the diagnostic yield of non‐magnified images in diagnosing esophageal neoplasia. The secondary aim was to compare HD endoscopy and non‐HD endoscopy in terms of diagnostic performance. Results: Overall, the sensitivity of NBI for screening of esophageal neoplasia was superior to WLI, and equivalent to iodine staining (92% vs 42%; P < 0.05, 92% vs 100%; ns). The specificity of NBI was equivalent to WLI (89% vs 94%; ns). In HD, NBI sensitivity was equivalent to both iodine staining and WLI (100% vs 75%; ns). In non‐HD, NBI sensitivity was equivalent to iodine staining, but WLI sensitivity was significantly inferior to NBI (88% vs 100%; ns, 25% vs 88%; P < 0.05). The NBI specificity was equivalent to WLI not only in HD but also in non‐HD (90% vs 96%; ns, 88% vs 93%; ns). Conclusion: In both HD and non‐HD endoscopy, NBI is less likely than WLI to miss a lesion. Even with non‐HD endoscopy, NBI is suitable for esophageal standard examinations in general hospitals.