Optical Endoscopy Research Articles

Optical System Design for Micro Medical Electronic Endoscope

The optical fibre endoscope with cold light is still mainstream in the endoscope market, but the inherent structural characteristics of the optical fibre endoscope lead to its shortcomings, such as high price, inconvenient to carry, and easy distortion of image. The micro medical electronic endoscope can receive the front-end optical system image through the miniature CCD (Charge Coupled Device) and transmit the image to the display through the cable, which greatly solves the limitations of the optical fibre endoscope. In this paper, using ZEMAX software, an optical imaging system with 75∘ field of view is designed. The system consists of four lenses, and all of them are standard spherical lenses. The maximum aperture is 2.2 mm and can match the 1/10-inch CCD. The distortion of the edge field of view is less than 20%, the aberration is small, and the light convergence is good. The maximum spatial resolution is 175 lp/mm.

High Accuracy Transmission and Recognition of Complex Images through Multimode Fibers Using Deep Learning

AbstractMultimode fiber shows tremendous potential in promoting the microminiaturization of optical endoscopes. However, multimode transmission is quite sensitive to fiber deformations and environmental changes. High‐accuracy transmission of complex images through a multimode fiber using traditional methods remains challenging research. Deep learning, which shows enormous vitality in optical imaging, may break through this limitation. Here, a deep neural network: U‐architecture speckles imaging network (USINET) is presented to realize high accuracy reconstruction of complex images under different multimode fiber transmission conditions. Furthermore, a shallow neural network: convolutional neural network (CNN)‐architecture speckles recognition network (CSRNET) is designed to realize high accuracy recognition for multiple categories of speckles at the output of multimode fiber under different bending states. The experimental results demonstrate that the proposed networks can realize high accuracy transmission and recognition of complex images through multimode fibers, which indicates the application prospect of multimode fibers combined with deep learning in minimally invasive medicine.

Alternating projection-based phase optimization for arbitrary glare suppression through multimode fiber

Wavefront shaping for glare suppression helps to reduce the speckle background through scattering media and enables imaging, sensing, and some speckle-related advanced applications through customizing the speckle light field. For glare suppression in a target region, current methods are either slow or not sufficiently generic. Here, an alternating projection method that fully exploits the transmission matrix of the scattering medium is proposed for fast and arbitrary glare suppression. Parallelly, multiple phase masks corresponding to different target regions can be computationally optimized without iterative hardware feedback. Numerical simulation shows that under phase-only modulation, a suppression factor of ∼10−3 can be realized for a large target region with only 30 iterations. With the use of a graphics processing unit and a digital micromirror device, fast and effective glare suppression for target regions of various shapes and sizes was demonstrated at the distal end of a multimode fiber. This technique could be promising for applications like multimode fiber-based speckle optical tweezer or endoscopy with speckle illumination inside complex environments.

The importance of follow-up examinations in chronic rhinosinusitis with nasal polyposis

PurposeClinical examinations following functional endoscopic sinus surgery (FESS) for chronic rhinosinusitis with nasal polyps (CRSwNP) are critical for physicians to assess results of the intervention and to early identify recurrences. However, no clear consensus on the frequency and timing of clinical examinations following surgery exists. The aim of this study was to analyze CRSwNP recurrences after FESS with a specific focus on the adherence to follow-up examinations. Materials and methodsSixty patients who underwent FESS for CRSwNP were enrolled. Clinical parameters were recorded. Adherence to follow-up examinations with nasal fiber optic endoscopy and regular administration of nasal steroids were analyzed. ResultsAdherence to periodic clinical examinations and regular treatment with nasal steroids was 25 %. CRSwNP recurrence was observed in 56.7 % of cases at the last follow-up examination. No statistically significant difference concerning nasal symptoms was observed between patients with and without current recurrence (p > 0.05). Subjects who underwent regular examinations and prompt treatment of small recurrences had a lower probability of relapse at their last examination (7.7 % versus 38.2 %, respectively; p < 0.001). Polyp grade > 2 in patients with or without adherence were seen in 15.4 % and 42.9 % of cases, respectively (p < 0.05). ConclusionsAdherence to follow-up examinations with nasal optic fiber endoscopy is crucial to early identify recurrence after surgery and promptly treat it with medical therapy.

Retrospective Analysis of Common Faults and Maintenance Strategies of Medical Electronic Endoscope

Medical electronic endoscope is one of the indispensable tools in medical diagnosis and treatment. With the development of science and technology, electronic endoscope has higher safety and accuracy than traditional optical endoscope. Due to the sophisticated construction and high price, hospitals spend a lot of money on maintenance every year. In order to prolong the working life of electronic endoscope, reduce the incidence of artificial failure and save hospital costs, this study made a retrospective analysis on the common faults of electronic endoscope, and summarized the maintenance strategies for reference.

Isolated hypopharynx lipoma: a case presentation and literature review

BackgroundLipomas are the most common benign mesenchymal tumors. They are defined as subcutaneous neoplasms of mature adipocyte cells that can occur wherever fatty tissue is. Lipomas are rare in the upper aerodigestive tract. Usually asymptomatic, they may be painful, uncomfortable, or even life-threatening especially if voluminous and located in the upper aerodigestive tract.Case presentationA 67-year-old female patient has presented with dyspnea on mild effort and chronic orthopnea. The physical examination was normal while the fiber optic endoscopy revealed a submucosal round-shaped mass rising from the left side of the post-cricoid region. CT scan revealed a well-circumscribed fatty mass of the left piriform sinus for which the patient underwent an endoscopic transoral approach for a complete removal with good results.Discussion and conclusionPharyngeal lipomas are rare entities that might be life-threatening. Although clinical manifestations are not specific, imaging techniques, especially MRI, help set the diagnosis showing a fatty mass of the upper aerodigestive tract. However, pathology examination is crucial to rule out low-grade liposarcomas. Surgical management is not well-codified and has benefited from the development of endoscopic techniques.

A planar micro rotary actuator for endoscopic optical scanning

Optical endoscopy is an essential technique for diagnosing disease in modern medicine. Side-viewing endoscopic probes with an embedded distal actuator that circumferentially scans an imaging light within an organ’s lumen are expected to significantly enhance the imaging ability of the probes. To this end, this work develops and experimentally analyzes an electromagnetic micro rotary actuator with a planar and hollow architecture. The actuator uses a liquid-phase bearing based on ferrofluid that is self-sustained on the magnetic rotor to eliminate complex bearing structures and enable low-friction actuation. Compared to preceding tubular designs, the planar topology allows for 83% downsizing in the actuator’s axial size, which helps preserve probe flexibility. Furthermore, the hollow design provides an unobstructed optical path through the actuator body, which removes imaging blind spots. A proof-of-concept scanner device is prototyped using flex-circuit microfabrication and 3D printing techniques for its electromechanical characterization. The prototype is successfully driven to revolve the rotor with 45° steps on a ring-shaped planar stator, which are then cycled at high frequencies to continuously spin the rotor up to a maximum rate of 2000 rpm with a device temperature below 45 °C, a safety threshold for tissue damage. The demonstrated stepwise and high-speed modes of laser scanning suggests the feasibility of the scanner design for multimodal imaging application toward advancing optical endoscope technology.

Femtosecond laser 3D printed micro objective lens for ultrathin fiber endoscope

The most important optical component in an optical fiber endoscope is its objective lens. To achieve a high imaging performance level, the development of an ultra-compact objective lens is thus the key to an ultra-thin optical fiber endoscope. In this work, we use femtosecond laser 3D printing to develop a series of micro objective lenses with different optical designs. The imaging resolution and field-of-view performances of these printed micro objective lenses are investigated via both simulations and experiments. For the first time, multiple micro objective lenses with different fields of view are printed on the end face of a single imaging optical fiber, thus realizing the perfect integration of an optical fiber and objective lenses. This work demonstrates the considerable potential of femtosecond laser 3D printing in the fabrication of micro-optical systems and provides a reliable solution for the development of an ultrathin fiber endoscope.

Usefulness of optical enhancement endoscopy combined with magnification to improve detection of intestinal metaplasia in the stomach.

Background and study aims The light blue crest observed in narrow band imaging endoscopy has high diagnostic accuracy for diagnosis of gastric intestinal metaplasia (GIM). The objective of this prospective study was to evaluate the diagnostic accuracy of magnifying i-scan optical enhancement (OE) imaging for diagnosing the LBC sign in patients with different levels of risk for gastric cancer in a Mexican clinical practice. Patients and methods Patients with a history of peptic ulcer and symptoms of dyspepsia or gastroesophageal reflux disease were enrolled. Diagnosis of GIM was made at the predetermined anatomical location and white light endoscopy and i-scan OE Mode 1 were captured at the two predetermined biopsy sites (antrum and pyloric regions). Results A total of 328 patients were enrolled in this study. Overall GIM prevalence was 33.8 %. The GIM distribution was 95.4 % in the antrum and 40.5 % in the corpus. According to the Operative Link on Gastritis/Intestinal-Metaplasia Assessment staging system, only two patients (1.9 %) were classified with high-risk stage disease. Sensitivity, specificity, positive​ and negative predictive values, positive and negative likelihood ratios, and accuracy of both methods (95 % C. I.) were 0.50 (0.41–0.60), 0.55 (0.48–0.62), 0.36 (0.31–0.42), 0.68 (0.63–0.73), 1.12 (0.9–1.4), 0.9 (0.7–1.1), and 0.53 (0.43–0.60) for WLE, and 0.96 (0.90–0.99), 0.91 (0.86–0.94), 0.84 (0.78–0.89), 0.98 (0.94–0.99), 10.4 (6.8–16), 0.05 (0.02–0.12), and 0.93 (0.89–0.95), respectively. The kappa concordance was 0.67 and the reliability coefficient was 0.7407 for interobserver variability. Conclusions Our study demonstrated the high performance of magnifying i-scan OE imaging for endoscopic diagnosis of GIM in Mexican patients.

Research on Resolution Enhancement Technology of Orthogonal Multimode Fiber Imaging

This paper presents a new scheme to improve the imaging resolution of optical fiber endoscope. Multimode fiber imaging is combined with correlation imaging experimental architecture, and Schmidt orthogonalization algorithm is used to reduce the correlation of light field. The simulation and experimental results show that this scheme can greatly improve the imaging quality and resolution, especially in the case of under sampling. In addition, the scheme can also resist the low resolution problem caused by the light field divergence of multimode fiber correlation imaging, and when the light field divergence reaches a certain extent, the resolution of the orthogonalized multimode fiber light field will no longer be affected. The feasibility of orthogonal multimode fiber imaging scheme in large depth of field is verified.

Gavan Edmund Rosman (1934–2022)

Gavan Rosman was valued at the Telecom (later Telstra) Research Laboratories, Australia, for his expertise as a research engineer in radio and coaxial cable technologies and, in particular, for his pioneering work on optical fibre technologies. He was also valued for his wide-ranging intellect and gentle, satirical sense of humour. His fluency in speaking Japanese was appreciated by visiting Japanese researchers. In retirement from TRL, he worked at Optiscan Imaging in Melbourne on developing an optical endoscope.

DI-CNG injector nozzle design influence on SI engine standard emissions and particulates at different injection timings

Compressed natural gas direct injection (DI-CNG) systems in spark ignition (SI) internal combustion engines have shown that it can give several benefits compared to CNG port fuel injection systems. However, the DI-CNG injector nozzle head design and gas jet formation may greatly influence engine exhaust gas emissions and performance. Present experimental study investigated the influence of 7 different nozzle head designs of spray-guided DI-CNG injectors on the combustion process, engine performance, standard emissions, and particulate number (PN) when methane fuel was injected at different injection timings (SOI) and injection pressures (18 bar and 50 bar). The nozzle heads had two main design patterns – heads with small multi holes/orifices and heads with larger crevices (swirl or umbrella spray pattern). Naturally aspirated SI engine tests were conducted at part load (6 bar IMEP) and wide-open throttle (WOT) at 2000 rpm engine speed. The results revealed that the difference between the nozzle heads was small when the fuel was injected at an early stage of the intake stroke (310–350 CAD bTDC) either at part load or high load. However, for late injection timing (130–190 CAD bTDC), the design of the DI-CNG injector nozzle head had a large impact on the combustion stability, standard emissions formation and particulates. Multi-hole nozzle heads showed improved CO2, CO, THC, total PN, and slightly higher NOx emissions compared to nozzle heads with larger crevices. For some of the nozzles, the SOI could be retarded more than for other injector head designs at higher injection pressure whilst still ensuring an acceptable engine performance in terms of combustion stability, power output and emissions formation. Overall, 50-bar injection pressure and a late injection timing under WOT conditions achieved higher engine load levels with all injector nozzle types. Images acquired using an optical endoscope technique with a high-speed video camera showed that a yellow flame was present for all nozzle types at a low injection pressure and late SOI. Increasing the injection pressure reduced the injection duration, improved air/fuel mixing which resulted in the reduced yellow flame formation and lower PN for most of the nozzle heads.

Scanning optimization of an electrothermally-actuated MEMS mirror for applications in optical coherence tomography endoscopy

Probe is an important component of the optical coherence tomography (OCT) system. Electrothermally-actuated micro-electromechanical (MEMS) mirrors are especially suitable for OCT endoscopic imaging due to their large scan angle, low driving voltage and high fill factor. However, endoscopic OCT imaging quality would be seriously affected by the nonlinear scanning characteristics of electrothermal MEMS mirrors as well as the distortion due to the need of placing the MEMS mirror on a 45° slope. In this work, an open-loop control method based on the transfer function of the MEMS mirror is proposed to optimize the overall optical trajectory scanned on the sample under a MEMS OCT probe. The transfer function of the electrothermal MEMS mirror is established and the relation between the MEMS mirror’s tilt angle and the final scanning trajectory on the sample is calculated. A PID control model based on the transfer function is developed and employed to generate the driving voltage signals that can be applied to the MEMS mirror for obtaining undistorted scanning trajectories on the sample. Experiments show that the proposed method can correct the scanning nonlinearity and the distortion without adding extra hardware. For instance, the linear scanning ratio is improved from 72% up to 98%; the fan-shaped distortion is reduced by a factor 3–5. This method is also applied to a swept-source OCT system and the image distortions are compensated effectively.

Three-dimensional light-field microendoscopy with a GRIN lens array.

Optical endoscopy has emerged as an indispensable clinical tool for modern minimally invasive surgery. Most systems primarily capture a 2D projection of the 3D surgical field. Currently available 3D endoscopes can restore stereoscopic vision directly by projecting laterally shifted views of the operating field to each eye through 3D glasses. These tools provide surgeons with informative 3D visualizations, but they do not enable quantitative volumetric rendering of tissue. Therefore, advanced tools are desired to quantify tissue tomography for high precision microsurgery or medical robotics. Light-field imaging suggests itself as a promising solution to the challenge. The approach can capture both the spatial and angular information of optical signals, permitting the computational synthesis of the 3D volume of an object. In this work, we present GRIN lens array microendoscopy (GLAM), a single-shot, full-color, and quantitative 3D microendoscopy system. GLAM contains integrated fiber optics for illumination and a GRIN lens array to capture the reflected light field. The system exhibits a 3D resolution of ∼100 µm over an imaging depth of ∼22 mm and field of view up to 1 cm2. GLAM maintains a small form factor consistent with the clinically desirable design, making the system readily translatable to a clinical prototype.

Design of Medical Optical Zoom Achromatic Endoscope Objective

Design of Medical Optical Zoom Achromatic Endoscope Objective

Sensitivity improved Cerenkov luminescence endoscopy using optimal system parameters.

The challenges of clinical translation of optical imaging, including the limited availability of clinically used imaging probes and the restricted penetration depth of light propagation in tissues can be avoided using Cerenkov luminescence endoscopy (CLE). However, the clinical applications of CLE are limited due to the low signal level of Cerenkov luminescence and the large transmission loss caused by the endoscope, which results in a relatively low detection sensitivity of current CLE. The aim of this study was to enhance the detection sensitivity of the CLE system and thus improve the system for clinical application in the detection of gastrointestinal diseases. Four optical fiber endoscopes were customized with different system parameters, including monofilament (MF) diameter of imaging fiber bundles, fiber material, probe coating, etc. The endoscopes were connected to the detector via a specifically designed straight connection device to form the CLE system. The β-2-[18F]-Fluoro-2-deoxy-D-glucose (18F-FDG) solution and the radionuclide of Gallium-68 (68Ga) were used to evaluate the performance of the CLE system. The images of the 18F-FDG solution acquired by the CLE were used to optimize imaging parameters of the system. By using the endoscope with optimized parameters, including the MF diameter of imaging fiber bundles, fiber materials, etc., the resolution and sensitivity of the assembled CLE system were measured by imaging the radionuclide of 68Ga. The results of 18F-FDG experiments showed that larger MF diameter led to higher collection efficiency. The fiber material and probe coating with high transmission ratios in the range of 400-900 nm also increased signal collection and transmission efficiency. The results of 68Ga evaluations showed that a minimum radioactive activity of radionuclides as low as 0.03 µCi was detected in vitro within 5 minutes, while that of 0.68 µCi can be detected within 1 minute. In vivo experiments also demonstrated that the developed CLE system achieved a high sensitivity at a submicrocurie level; that is, 0.44 µCi within 5 minutes, and 0.83 µCi within 1 minute. The weaker in vivo sensitivity was due to the attenuation of the signal by the mouse tissue skin and the autofluorescence interference produced by biological tissues. By optimizing the structural parameters of fiber endoscope and imaging parameters for data acquisition, we developed a CLE system with a sensitivity at submicrocurie level. These results support the possibility that this technology can clinically detect early tumors within 1 minute.

Video-rate dual-modal photoacoustic and fluorescence imaging through a multimode fibre towards forward-viewing endomicroscopy

Multimode fibres (MMFs) are becoming increasingly attractive in optical endoscopy as they promise to enable unparallelled miniaturisation, spatial resolution and cost. However, high-speed imaging with wavefront shaping has been challenging. Here, we report the development of a video-rate dual-modal photoacoustic (PA) and fluorescence microscopy probe with a high-speed digital micromirror device (DMD) towards forward-viewing endomicroscopy. Optimal DMD patterns were obtained using a real-valued intensity transmission matrix algorithm to raster-scan a 1.5 μm-diameter focused beam at the distal fibre tip for imaging. The PA imaging speed and spatial resolution were varied from ∼2 to 57 frames per second and from 1.7 to 3 μm, respectively. Further, high-fidelity PA images of carbon fibres and mouse red blood cells were acquired at unprecedented speed. The capability of dual-modal imaging was demonstrated with phantoms. We anticipate that with further miniaturisation of the ultrasound detector, this probe could be integrated into medical needles to guide minimally invasive procedures.

Diagnostic efficacy of the Japan NBI Expert Team classification with dual-focus magnification for colorectal tumors.

The Japan NBI Expert Team (JNET) classification is the first unified classification criteria for colorectal tumors using magnifying narrow-band imaging (NBI) in Japan. However, the diagnostic stratification ability of the JNET classification with dual-focus magnifying NBI (DF-JNET) has remained obscure. The aim of this study was to validate the diagnostic stratification ability of DF-JNET for colorectal tumors in two Japanese referral centers. A multicenter retrospective image evaluation study was conducted by three experienced endoscopists, including an original JNET member who was also involved in establishing the diagnostic criteria. A total of two images, namely, one representative non-magnified white light image and one representative DF-NBI image for each of the 557 consecutive lesions were used in the evaluation study. The diagnostic value of DF-JNET was calculated based on the evaluation data. The sensitivity, specificity, positive and negative predictive values, and accuracy of DF-JNET Type 1 for differentiating between non-neoplastic and neoplastic lesions were 78.1%, 98.6%, 89.1%, 96.8%, and 95.9%, respectively; of Type 2A lesions for differentiating low-grade dysplasia from others were 98.0%, 76.5%, 94.9%, 89.7%, and 94.1%, respectively; of Type 2B lesions for differentiating high-grade dysplasia and shallow submucosal invasive carcinoma from others were 43.5%, 99.1%, 66.7%, 97.6%, and 96.8%, respectively; and of Type 3 lesions for differentiating deep submucosal invasive carcinoma from others were 83.3%, 99.5%, 62.5%, 99.8%, and 99.3%, respectively. All DF-JNET types had an over 90% diagnostic accuracy for the histological prediction of colorectal tumors. DF-JNET might contribute to appropriate treatment choices, such as endoscopic resection or surgery, not only in Japan but also in Western countries in which the use of optical zoom endoscopy is limited.

Research on passive low-light-level optical fiber endoscope detection system

A passive low-light-level optical fiber endoscope detection imaging system is studied by combining optical fiber endoscope technology with high sensitivity EMCCD low-light-level imaging technology. On the basis of designing the overall system, the hardware with dual-mode switching function is constructed by using ordinary color camera and low-light-level camera. The USAF1951 resolution board is used to test the resolution of the system. The results show the white light lateral resolution of the system of 70.1 µm, the night vision lateral resolution of 180 µm. The average value of Bhattacharyya coefficient is 0.8681, indicating that the system can effectively avoid light leakage. In the environment of illuminance of 0.5 Lux, the image frame rate of the system is greater than 25 Hz, indicating that the system has fast imaging speed under low illumination. The imaging gain of the system can be up to 1000 times, indicating that the high-sensitivity low-illuminance camera has excellent imaging ability under low light conditions. After calculation, the system has a field of view of 66.4 cm2, which is more suitable for observing rodents. The passive low-light-level optical fiber endoscope detection imaging system has highly sensitive detection performance under weak light environment such as rodent caves, where active lighting is not suitable.

Application of Current Image-Enhanced Endoscopy in Gastric Diseases

Image-enhanced endoscopy (IEE) plays an integral role in endoscopic diagnosis and treatment. IEE enables an early and accurate detection of cancer and characterization of lesions prior to therapeutic decisions. Ideal IEE can serve as an optical or digital chromoscopic endoscopy, as well as an optical biopsy that predicts exact histopathology. Several IEE modalities have recently been developed and are used in the clinical field. The stomach is a challenging organ for imaging because of its complex secretion function and status of Helicobacter pylori infection. Therefore, understanding the current IEE modalities for their clinical applicability in an evidence-based approach is warranted. Along with technology refinements, the new paradigm will be available for the diagnosis of gastric cancer or other conditions in the stomach in the near future.