Endoscopic Probe Research Articles

Dual-camera endoscopic imaging probe combining simultaneous illumination of white-light and laser sources for near real-time monitoring of tissue features

In this work, a dual-display endoscopic vision system was designed as a multi-parametric tool to monitor dynamic responses of biological tissues. The endoscope integrates oximetry principles, laser speckles imaging, and image fusion processing to simultaneously monitor hemodynamic and metabolic information with high spatial resolution. In addition, morphological changes of the tissue were evaluated using linear approximation to Rayleigh-MIE scattering over the visible range. The setup contains a white light source (QTH lamp), an NIR laser (810 nm), commercially available endoscope, high speed four position filter wheel, and two CCD cameras (color and monochromatic) for near real-time processing and display. Validation of the system was demonstrated in two models of tissue injury challenge, including a drug toxicity experiment conducted on a mouse model and the artery occlusion of a human finger. The experimental results illustrate the ability of our system to simultaneously map and temporally track changes in tissue parameters which has the potential to provide valuable insight into the physiological state of the tissue during endoscopic surgical procedures, making it attractive in the future for use in clinical practice and research applications.

Changes in Distensibility Index During an Incremental POEM Myotomy

BackgroundA longer myotomy for the treatment of achalasia is associated with worse gastroesophageal reflux disease despite palliating dysphagia. Recently, clinical outcomes have been correlated to the distensibility of the distal esophagus, which is measured intra-operatively using an endoscopic functional luminal image probe (EndoFLIP). We aimed to determine the minimum per oral endoscopic myotomy (POEM) length to allow for adequate distensibility index (DI). MethodsA 6-cm myotomy conducted in 2-cm increments during POEM was performed for patients with achalasia I and II from 2017 to 2019. The EndoFLIP was used to measure the DI intra-operatively: (1) prior to intervention, (2) following creation of the submucosal tunnel, (3) following transection of the high-pressure zone (HPZ), (4) following the distal extension, and (5) following the proximal esophageal extension. ResultsA total of 16 patients underwent POEM. Ages ranged from 21 to 78 years, 10 were male, and 13 had type II achalasia. The median DI was 2.7 (1.4–3.6) mm2/mmHg prior to intervention; 2.4 (1.4–3.3) mm2/mmHg following the submucosal tunnel; 3.2 (1.6–4.4) mm2/mmHg following transection of the HPZ; 3.8 (2.6–4.5) mm2/mmHg following the gastric extension; and 4.5 (3.3–7.1) mm2/mmHg following the proximal extension. Our target range DI was achieved for 50% of patients after transection of the HPZ. ConclusionsDistensibility changed with each myotomy increment and fell within the target range for most patients following a 2–4-cm myotomy. This suggests that a shorter myotomy may be appropriate for select patients, and the use of the EndoFLIP intra-operatively may allow for a tailored myotomy length.

Assessment of Murine Colon Inflammation Using Intraluminal Fluorescence Lifetime Imaging.

Inflammatory bowel disease (IBD) is typically diagnosed by exclusion years after its onset. Current diagnostic methods are indirect, destructive, or target overt disease. Screening strategies that can detect low-grade inflammation in the colon would improve patient prognosis and alleviate associated healthcare costs. Here, we test the feasibility of fluorescence lifetime imaging (FLIm) to detect inflammation from thick tissue in a non-destructive and label-free approach based on tissue autofluorescence. A pulse sampling FLIm instrument with 355 nm excitation was coupled to a rotating side-viewing endoscopic probe for high speed (10 mm/s) intraluminal imaging of the entire mucosal surface (50–80 mm) of freshly excised mice colons. Current results demonstrate that tissue autofluorescence lifetime was sensitive to the colon anatomy and the colonocyte layer. Moreover, mice under DSS-induced colitis and 5-ASA treatments showed changes in lifetime values that were qualitatively related to inflammatory markers consistent with alterations in epithelial bioenergetics (switch between -oxidation and aerobic glycolysis) and physical structure (colon length). This study demonstrates the ability of intraluminal FLIm to image mucosal lifetime changes in response to inflammatory treatments and supports the development of FLIm as an in vivo imaging technique for monitoring the onset, progression, and treatment of inflammatory diseases.

All-fiber negative axicon probe with a Bessel beam for cellular-level low coherence phase microscopy and refractive index measurement.

We demonstrate an all-fiber negative axicon probe with a Bessel beam for low coherence phase microscopy including refractive index measurement of a cellular level sample in reflection mode. The negative axicon chemically incised at the distal end of the optical fiber spawns the Bessel beam. The system provides a phase sensitivity of ∼0.28 mrad and optical path length sensitivity of ∼23 pm in air. The lateral resolution and working distance are found to be ∼3.91 µm and 650 µm to exhibit the performance of the system experimentally. The three-dimensional (3D) phase map of the cheek cell along with the refractive index is obtained from the reflected power spectrum. The combined low coherence phase microscopy and refractive index measurement provides the system with a potential for biological application. Also, the all-fiber probe can be easily integrated as an endoscopic probe.

Esophageal Virtual Disease Landscape Using Mechanics-Informed Machine Learning

The pathogenesis of esophageal disorders is related to the esophageal wall mechanics. Therefore, to understand the underlying fundamental mechanisms behind various esophageal disorders, it is crucial to map the esophageal wall mechanics-based parameters onto physiological and pathophysiological conditions corresponding to altered bolus transit and supraphysiologic IBP. In this work, we present a hybrid framework that combines fluid mechanics and machine learning to identify the underlying physics of the various esophageal disorders and maps them onto a parameter space which we call the virtual disease landscape (VDL). A one-dimensional inverse model processes the output from an esophageal diagnostic device called endoscopic functional lumen imaging probe (EndoFLIP) to estimate the mechanical health of the esophagus by predicting a set of mechanics-based parameters such as esophageal wall stiffness, muscle contraction pattern and active relaxation of esophageal walls. The mechanics-based parameters were then used to train a neural network that consists of a variational autoencoder (VAE) that generates a latent space and a side network that predicts mechanical work metrics for estimating esophagogastric junction motility. The latent vectors along with a set of discrete mechanics-based parameters define the VDL and form clusters corresponding to the various esophageal disorders. The VDL not only distinguishes different disorders but can also be used to predict disease progression in time. Finally, we also demonstrate the clinical applicability of this framework for estimating the effectiveness of a treatment and track patient condition after a treatment.

Beyond images: Emerging role of Raman spectroscopy-based artificial intelligence in diagnosis of gastric neoplasia.

White-light endoscopy with tissue biopsy is the gold standard interface for diagnosing gastric neoplastic lesions. However, misdiagnosis of lesions is a challenge because of operator variability and learning curve issues. These issues have not been resolved despite the introduction of advanced imaging technologies, including narrow band imaging, and confocal laser endomicroscopy. To ensure consistently high diagnostic accuracy among endoscopists, artificial intelligence (AI) has recently been introduced to assist endoscopists in the diagnosis of gastric neoplasia. Current endoscopic AI systems for endoscopic diagnosis are mostly based upon interpretation of endoscopic images. In real-life application, the image-based AI system remains reliant upon skilful operators who will need to capture sufficiently good quality images for the AI system to analyze. Such an ideal situation may not always be possible in routine practice. In contrast, non-image-based AI is less constraint by these requirements. Our group has recently developed an endoscopic Raman fibre-optic probe that can be delivered into the gastrointestinal tract via the working channel of any endoscopy for Raman measurements. We have also successfully incorporated the endoscopic Raman spectroscopic system with an AI system. Proof of effectiveness has been demonstrated in in vivo studies using the Raman endoscopic system in close to 1,000 patients. The system was able to classify normal gastric tissue, gastric intestinal metaplasia, gastric dysplasia and gastric cancer, with diagnostic accuracy of >85%. Because of the excellent correlation between Raman spectra and histopathology, the Raman-AI system can provide optical diagnosis, thus allowing the endoscopists to make clinical decisions on the spot. Furthermore, by allowing non-expert endoscopists to make real-time decisions as well as expert endoscopists, the system will enable consistency of care.

Impedance planimetry (EndoFLIP) measurements persist long term after anti-reflux surgery

PurposeThe functional lumen imaging probe provides objective measurements of the gastroesophageal junction during laparoscopic anti-reflux surgery. There is a lack of data on how functional lumen imaging probe measurements change at follow-up. We aim to describe our institutional experience in performing functional lumen imaging probe during postoperative endoscopy after laparoscopic anti-reflux surgery. MethodsA prospectively maintained database was queried. Patients who had postoperative endoscopic functional lumen imaging probe measurements between March 2018 and June 2021 were assessed at different time points from their index laparoscopic anti-reflux surgery using paired t test. Standardized quality of life questionnaires were collected for up to 2 years. Group comparisons were made using the Wilcoxon rank-sum test. ResultsFifty-eight patients who underwent laparoscopic anti-reflux surgery (magnetic sphincter augmentation or fundoplication) had postoperative functional lumen imaging probe. Thirty-two intraoperative functional lumen imaging probe values were compared with their postoperative functional lumen imaging probe. Fundoplication values did not differ. Postoperative functional lumen imaging probe distensibility index for magnetic sphincter augmentation patients was decreased (P = .04). Functional lumen imaging probe measurements for all postoperative endoscopies showed that magnetic sphincter augmentation had the lowest distensibility index (P < .01). Dysphagia as a reason for endoscopy had a decrease in distensibility index (P = .03). ConclusionFunctional lumen imaging probe measurements after fundoplication persist at long-term follow up while patients may have a tighter gastroesophageal junction after magnetic sphincter augmentation. Functional lumen imaging probe has the potential to assess the success or failure after laparoscopic anti-reflux surgery and optimize patient outcomes.

Automatic correction of the initial rotation angle error improves 3D reconstruction in endoscopic airway optical coherence tomography.

Endoscopic airway optical coherence tomography (OCT) is an advanced imaging modality capable of capturing the internal anatomy and geometry of the airway. Due to fiber-optic catheter bending and friction, the rotation speed of the endoscopic probe is usually non-uniform: at each B-scan image, the initial rotation angle of the probe is easily misaligned with that of the previous slices. During the pullback operation, this initial rotation angle error (IRAE) will be accumulated and will result in distortion and deformation of the reconstructed 3D airway structure. Previous attempts to correct this error were mainly manual corrections, which are time-consuming and suffered from observer variation. In this paper, we present a method to correct the IRAE for anatomically improved visualization of the airway. Our method derived the rotation angular difference of adjacent B-scans by measuring their contour similarity and then tracks the IRAE by formulating its continuous drift as a graph-based problem. The algorithm was tested on a simulated airway contour dataset, and also on experimental datasets acquired by two different long range endoscopic airway OCT platforms. Effective and smooth compensation of the frame-by-frame initial angle difference was achieved. Our method has real-time capability and thus has the potential to improve clinical imaging efficiency.

The Feasibility of Haar Feature-Based Endoscopic Ultrasound Probe Tracking for Implanting Hydrogel Spacer in Radiation Therapy for Pancreatic Cancer.

PurposeWe proposed a Haar feature-based method for tracking endoscopic ultrasound (EUS) probe in diagnostic computed tomography (CT) and Magnetic Resonance Imaging (MRI) scans for guiding hydrogel injection without external tracking hardware. This study aimed to assess the feasibility of implementing our method with phantom and patient images.Materials and MethodsOur methods included the pre-simulation section and Haar features extraction steps. Firstly, the simulated EUS set was generated based on anatomic information of interpolated CT/MRI images. Secondly, the efficient Haar features were extracted from simulated EUS images to create a Haar feature dictionary. The relative EUS probe position was estimated by searching the best matched Haar feature vector of the dictionary with Haar feature vector of target EUS images. The utilization of this method was validated using EUS phantom and patient CT/MRI images.ResultsIn the phantom experiment, we showed that our Haar feature-based EUS probe tracking method can find the best matched simulated EUS image from a simulated EUS dictionary which includes 123 simulated images. The errors of all four target points between the real EUS image and the best matched EUS images were within 1 mm. In the patient CT/MRI scans, the best matched simulated EUS image was selected by our method accurately, thereby confirming the probe location. However, when applying our method in MRI images, our method is not always robust due to the low image resolution.ConclusionsOur Haar feature-based method is capable to find the best matched simulated EUS image from the dictionary. We demonstrated the feasibility of our method for tracking EUS probe without external tracking hardware, thereby guiding the hydrogel injection between the head of the pancreas and duodenum.

Optical Fiber Coupling System for Steerable Endoscopic Instruments.

In this paper, we present an optical coupling system that couples light from an Endostat fiber in a commercial laser surgical system into a smaller multimode fiber, in order to enable endoscopic probe steering in a tightly confined space. Unlike the Endostat fibers, which have a minimum bending radius of 12 mm due to the large diameter, our work allows the laser to be delivered by smaller fibers that can be readily bent at a 6-mm bending radius by a distal steerable mechanism. Such a readily achievable sharp bending facilitates the surgical laser to access hard-to-reach anatomies. We experimentally achieved an optical power coupling efficiency of ≈ 50%. Tissue ablation experiments were performed to prove the feasibility and potential of our light coupling system in clinical laser surgeries, as well as other optical fiber-based endoscopic medical devices.Clinical Relevance- Optical fibers are commonly used in laser-based surgical systems. The optical coupling system in this paper enables the laser to be delivered by small fibers, helps realize the fiber bending and steering, and hence allows the laser treatments of previous inaccessible anatomies.

S1450 Use of Endoscopic Functional Lumen Imaging Probe (EndoFLIP®) to Assess Pyloric Sphincter Function: A Pilot Study in Subjects With and Without Gastroparesis

S1450 Use of Endoscopic Functional Lumen Imaging Probe (EndoFLIP®) to Assess Pyloric Sphincter Function: A Pilot Study in Subjects With and Without Gastroparesis

Endomicroscopy of the human cochlea using a micro-optical coherence tomography catheter

Sensorineural hearing loss (SNHL) is one of the most profound public health concerns of the modern era, affecting 466 million people today, and projected to affect 900 million by the year 2050. Advances in both diagnostics and therapeutics for SNHL have been impeded by the human cochlea’s inaccessibility for in vivo imaging, resulting from its extremely small size, convoluted coiled configuration, fragility, and deep encasement in dense bone. Here, we develop and demonstrate the ability of a sub-millimeter-diameter, flexible endoscopic probe interfaced with a micro-optical coherence tomography (μOCT) imaging system to enable micron-scale imaging of the inner ear’s sensory epithelium in cadaveric human inner ears.

Epistaxis Secondary to Rhinolith: A Forgotten and Scarce Entity

Rhinolith is a calcareous concretion resulting from mineralization and encrustation of an endogenous or exogenous nidus in the nose. This rare clinical entity could be the result of a previous introduction of a foreign body into the nasal cavity. Rhinolith is rarely seen by the clinical practitioner. We report a case of rhinolith in a young healthy lady who presented with epistaxis and highlight the clinical presentation and management of this case. The history of foreign body insertion may be overlooked in such cases. Presence of grittiness on endoscopic probing aid in establishing the diagnosis. Early referral from primary care centre to ENT can avoid misdiagnosis and further complications as removal of the rhinolith is the ultimate treatment.

Subcutaneous Vulvar Flap Viability Evaluation With Near-Infrared Probe and Indocyanine Green for Vulvar Cancer Reconstructive Surgery: A Feasible Technique.

Introduction: Vulvar cancer is a rare condition affecting older women and accounts for 3–5% of all gynecological cancers. Primary surgical treatment involves the removal of a large amount of tissue for which reconstructive surgery is often necessary with a high rate of postoperative complications. Despite several techniques for the evaluation of vulvar flap viability have been proposed, many methods cannot be performed during surgery and require expensive devices often missing in a gynecological clinic. This study aims to verify the feasibility and the safety of the vulvar flap viability evaluation through a near-infrared endoscopic probe and Indocyanine green (ICG) tracer in a small group of patients and to evaluate long-term vulvar flap outcomes.Methods: Patients with primary vulvar cancer who required surgical treatment and subsequent vulvar flap reconstructive surgery were prospectively included in the study. A 25 mg ICG vial diluted in 20 ml of saline solution was intravenously infused before closing the skin edges of the flaps. All patients were given 0.2 mg/kg body weight of intravenous ICG. After 10–15 min, a near-infrared endoscopic probe was used to evaluate the vulvar flap viability.Results: Of the 18 patients who underwent radical vulvectomy for vulvar cancer during the study period, 15 were included in the analysis. All packaged surgical flaps showed tracer uptake on the surgical margin. No intro-operative complications were recorded neither surgery-related nor to dye infusion. No surgical infection, dehiscence, or necrosis was recorded.Conclusions: Vulvar flap viability assessment using Indocyanine green and a laparoscopic infrared probe is a feasible method. All cases included in the analysis showed a dye uptake on the surgical edge of the flap. Further, prospective studies are needed to confirm the method in clinical practice and to evaluate its superiority over simple subjective clinical evaluation.

Sub millimetre flexible fibre probe for background and fluorescence free Raman spectroscopy.

Using the shifted-excitation Raman difference spectroscopy technique and an optical fibre featuring a negative curvature excitation core and a coaxial ring of high numerical aperture collection cores, we have developed a portable, background and fluorescence free, endoscopic Raman probe. The probe consists of a single fibre with a diameter of less than 0.25 mm packaged in a sub-millimetre tubing, making it compatible with standard bronchoscopes. The Raman excitation light in the fibre is guided in air and therefore interacts little with silica, enabling an almost background free transmission of the excitation light. In addition, we used the shifted-excitation Raman difference spectroscopy technique and a tunable 785 nm laser to separate the fluorescence and the Raman spectrum from highly fluorescent samples, demonstrating the suitability of the probe for biomedical applications. Using this probe we also acquired fluorescence free human lung tissue data.

Current management of pediatric achalasia.

Achalasia is a rare condition affecting esophageal motility in children. In a manner similar to the disease found in the adult population, children experience symptoms of dysphagia, regurgitation, and chest pain due to a failure of relaxation of the lower esophageal sphincter. Standard diagnostic approaches include upper endoscopy and esophageal manometry. New developments in diagnosis include high-resolution esophageal manometry and the endoscopic functional lumen imaging probe. Therapies available include endoscopic balloon dilations and botulinum toxin injections into the lower esophageal sphincter, as well as surgical interventions. The Heller myotomy was first described in 1913; since then, there have been many modifications to the procedure to improve outcomes and lower morbidity. Currently, the most commonly performed surgical procedure is the laparoscopic Heller myotomy, in which the sphincter muscle is divided using longitudinal incisions with or without a partial fundoplication procedure. In recent years, per oral endoscopic myotomy (POEM) is gaining support as a viable natural orifice therapy for achalasia. Complications of POEM occur at a relatively low rate, and outcomes following the procedure have been promising. The treatment of end-stage achalasia however, may include partial or total esophagectomy with reconstruction if possible. Future research is focused primarily on increasing the efficacy, and lowering complications, of existing therapeutic modalities.

Advances in Endoscopic Photoacoustic Imaging.

Photoacoustic (PA) imaging is able to provide extremely high molecular contrast while maintaining the superior imaging depth of ultrasound (US) imaging. Conventional microscopic PA imaging has limited access to deeper tissue due to strong light scattering and attenuation. Endoscopic PA technology enables direct delivery of excitation light into the interior of a hollow organ or cavity of the body for functional and molecular PA imaging of target tissue. Various endoscopic PA probes have been developed for different applications, including the intravascular imaging of lipids in atherosclerotic plaque and endoscopic imaging of colon cancer. In this paper, the authors review representative probe configurations and corresponding preclinical applications. In addition, the potential challenges and future directions of endoscopic PA imaging are discussed.

A Side-Viewing Endoscopic Probe With Distal Micro Rotary Scanner for Multimodal Luminal Imaging and Analysis

This paper reports a novel micro electromagnetic actuator serving as the distal rotary scanner of an endoscopic probe developed for side-viewing luminal tissue screening and analysis enabled through different endoscopic modalities. The micro rotary optical scanner, for the first time, offers stepwise, low-speed, and high-speed rotational motions to be compatible with endoscopic optical coherence tomography (OCT) and Raman spectroscopy. In comparison with preceding designs, this rotary scanner is shown to provide up to 125× higher revolution speeds per power via a ~50% narrower body while limiting its operation temperature within a biologically safe level for in-vivo scanning purposes. A preliminary experiment on human skin tissues is performed using the prototyped side-viewing OCT endoscopic probe equipped with the developed distal scanner. The results demonstrate the probe's ability for real-time 360° imaging of live tissue with both high speed and high resolution. These results pave the path for further testing on human internal lumens.

Endotherapy for Nonvariceal Upper Gastrointestinal Hemorrhage

AbstractNonvariceal upper gastrointestinal hemorrhage (NVUGIH) is a common GI emergency with significant morbidity and mortality. Triaging cases on the basis of patient-related factors, restrictive blood transfusion strategy, and hemodynamic stabilization are key initial steps for the management of patients with NVUGIH. Endoscopy remains a vital step for both diagnosis and definitive management. Multiple studies and guidelines have now defined the optimum timing for performing the endoscopy after hospitalization, to better the outcome. Conventional methods for achieving endoscopic hemostasis, such as injection therapy, contact, and noncontact thermal therapy, and mechanical therapy, such as through-the-scope clips, have reported to have 76 to 90% efficacy for primary hemostasis. Newer modalities to enhance hemostasis rates have come in vogue. Many of these modalities, such as cap-mounted clips, coagulation forceps, and hemostatic powders have proved to be efficacious in multiple studies. Thus, the newer modalities are recommended not only for management of persistent bleed and recurrent bleed after failed initial hemostasis, using conventional modalities but also now being advocated for primary hemostasis. Failure of endotherapy would warrant radiological or surgical intervention. Some newer tools to optimize endotherapy, such as endoscopic Doppler probes, for determining flow in visible or underlying vessels in ulcer bleed are now being evaluated. This review is focused on the technical aspects and efficacy of various endoscopic modalities, both conventional and new. A synopsis of the various studies describing and comparing the modalities have been outlined. Postendoscopic management including Helicobacter pylori therapy and starting of anticoagulants and antiplatelets have also been outlined.

Wide Field-of-View, High-Resolution Endoscopic Lens Design with Low F-Number for Disposable Endoscopy

In the past few decades, video endoscopy has become one of the primary medical devices in diverse clinical fields for examination, treatment, and early disease diagnosis of the gastrointestinal tract. For an accurate diagnosis, an endoscopic camera offering bright and wide field-of-view images is required while maintaining its compact dimensions to enter the long, narrow, and dark tract inside of the body. Recent endoscopic lenses successfully provide wide fields-of-view and have compact sizes for the system; however, their f-numbers still remain at 2.8 or higher. Therefore, further improvement in f-numbers is required to compensate for the restricted illumination system of the endoscopic probe. Here, we present a low f-number endoscopic lens design while providing wide field-of-view and high-resolution imaging. The proposed lens system achieved a low f-number of 2.2 and a field-of-view of 140 deg. The modulation transfer function (MTF) is over 20% at 180 lp/mm, and relative illumination is more than 60% in the full field. Additionally, the proposed lens is designed for a 1/4” 5-megapixel complementary metal-oxide-semiconductor (CMOS) image sensor with a pixel size of 1.4 µm. This all-plastic lens design could help develop a high-performance disposable endoscope that prevents the risk of infection or cross-contamination with mass manufacture and low cost.