Fiber Endoscope Research Articles

Shape sensing endoscope fiber

Minimally invasive and robotic surgeries are growing areas that benefit patients through reduced recovery time. Medical fiber optics play an important role in these procedures by enabling instrument navigation, imaging, sensing, power delivery, and diagnostics in a small form factor. One route to further miniaturization is to combine these functions, or a subset of these functions, into a single strand of optical fiber. In this work, we present a fiber and fan-in device that enables shape sensing, imaging, power delivery, and potentially additional sensing capabilities, such as temperature and/or pressure, in the same waveguide. The refractive index profile of the multimode waveguide in our fiber is similar to step index fibers used in laser delivery and is suitable for imaging applications; however, it also contains seven single mode cores twisted in a helix and with quasi-continuous Bragg gratings along their entire length, such as are used in fiber shape sensing. We first calibrate the transmission matrix of the multimode waveguide to enable the formation of a focused spot at the distal end of the fiber with a spatial light modulator. A second calibration allows us to reconstruct the shape of the fiber using optical frequency domain reflectometry in the twisted shape sensing cores. We show that these multiple functions can be performed simultaneously with our device and that changes in the curvature of the fiber correlate with the quality of the distal spot produced through the fiber, which is an important step towards maintaining the imaging calibration as the fiber is manipulated.

Advanced optical imaging techniques for bladder cancer detection and diagnosis: a systematic review.

To systematically assess the current available literature concerning advanced optical imaging methods for the detection and diagnosis of bladder cancer (BCa), focusing particularly on the sensitivity and specificity of these techniques. First a scoping search was performed to identify all available optical techniques for BCa detection and diagnosis. The optical imaging techniques used for detecting BCa are: the Storz professional image enhancement system (IMAGE1 S), narrow-band imaging (NBI), photoacoustic imaging (PAI), autofluorescence imaging (AFI), photodynamic diagnosis (PDD), and scanning fibre endoscopy (SFE). The staging and grading techniques for BCa are: optical coherence tomography (OCT), confocal laser endomicroscopy (CLE), Raman spectroscopy, endocytoscopy, and non-linear optical microscopy (NLO). Then a systematic literature search was conducted using MEDLINE, EMBASE and Web of Science from inception to 21 November 2023. Articles were screened and selected by two independent reviewers. Inclusion criteria were: reporting on both the sensitivity and specificity of a particular technique and comparison to histopathology, and in the case of a detection technique comparison to white light cystoscopy (WLC). Out of 6707 articles, 189 underwent full-text review, resulting in 52 inclusions. No articles met criteria for IMAGE1 S, PAI, SFE, Raman spectroscopy, and endocytoscopy. All detection techniques showed higher sensitivity than WLC, with NBI leading (87.8-100%). Overall, detection technique specificity was comparable to WLC, with PDD being most specific (23.3-100%). CLE and OCT varied in sensitivity and specificity, with OCT showing higher specificity for BCa diagnosis, notably for carcinoma in situ (97-99%) compared to CLE (62.5-81.3%). NLO demonstrated high sensitivity and specificity (90-97% and 77-100%, respectively) based on limited data from two small ex vivo studies. Optical techniques with the most potential are PDD for detecting and OCT for staging and grading BCa. Further research is crucial to validate their integration into routine practice and explore the value of other imaging techniques.

Ptychographic imaging with a fiber endoscope via wavelength scanning

Ptychography has become a popular computational imaging method for microscopy in recent years. In the present work we employ a wavelength scanning ptychography technique enhanced by neural networks for imaging with a fiber endoscope. Illumination of the object at various wavelengths is achieved using a single mode fiber, while a multicore fiber collects diffracted light from a distance. Using a U-Net multilayer convolutional neural network, the diffraction pattern is recovered at the far end of the multicore fiber from the recorded intensity pattern at the proximal end. With the recovered diffraction pattern in place, the phase object can be reconstructed using the ptychography algorithm. The quality of the object reconstruction improves with the number of wavelengths used. Comparison with an end-to-end neural network highlights the effectiveness and practicality of this two-step hybrid system. This alternative and simplified ptychographic endoscopy setup delivers noticeable improvements through neural networks and wavelength scanning.

Targeted detection of Barrett’s neoplasia: A case report

Barrett’s esophagus (BE) is a precursor condition for esophageal adenocarcinoma (EAC). This case report describes the in vivo use of a fluorescently-labeled peptide heterodimer specific for epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor (HER2) to identify residual neoplasia in a 52-year-old female patient with BE. This targeted contrast agent was topically administered after an incomplete endoscopic mucosal resection of high-grade dysplasia with carcinoma in situ. A flexible fiber-coupled multi-modal scanning fiber endoscope was used to capture near-infrared fluorescence images. This instrument was passed through the working channel of a standard upper endoscope for use as an accessory. Increased fluorescence intensity was observed from nodular mucosa as a real-time “red flag” to identify the presence of neoplasia. Pathologic tests were conducted on the resected tissues, confirming the presence of stage T1a EAC. The expression EGFR and HER2 was confirmed by immunohistochemistry ex vivo. These findings support integrated imaging as a potential strategy to detect Barrett’s neoplasia.

Optical fiber bundle differential compressive imaging.

We present a differential compressive imaging method for an optical fiber bundle (OFB), which provides a solution for an ultrathin bend-resistant endoscope with high resolution. This method uses an OFB and a diffuser to generate speckle illumination patterns. Differential operation is additionally applied to the speckle patterns to produce sensing matrices, by which the correlation between the matrices is greatly reduced from 0.875 to 0.0275, which ensures the high quality of image reconstruction. Pixilation artifacts from the fiber core arrangement are also effectively eliminated with this configuration. We demonstrate high-resolution reconstruction of images of 132 × 132 pixels with a compression rate of 12% using 77 fiber cores, the total diameter of which is only about 91 µm. An experimental verification proves that this method is tolerant to a limited degree of fiber bending, which provides a potential approach for robust high-resolution fiber endoscopy.

Double-Clad Antiresonant Hollow-Core Fiber and Its Comparison with Other Fibers for Multiphoton Micro-Endoscopy.

Label-free and multiphoton micro-endoscopy can transform clinical histopathology by providing an in situ tool for diagnostic imaging and surgical treatment in diseases such as cancer. Key to a multiphoton imaging-based micro-endoscopic device is the optical fiber, for distortion-free and efficient delivery of ultra-short laser pulses to the sample and effective signal collection. In this work, we study a new hollow-core (air-filled) double-clad anti-resonant fiber (DC-ARF) as a high-performance candidate for multiphoton micro-endoscopy. We compare the fiber characteristics of the DC-ARF with a single-clad anti-resonant fiber (SC-ARF) and a solid core fiber (SCF). In this work, while the DC-ARF and the SC-ARF enable low-loss (<0.2 dBm-1), close to dispersion-free excitation pulse delivery (<10% pulse width increase at 900 nm per 1 m fiber) without any induced non-linearities, the SCF resulted in spectral broadening and pulse-stretching (>2000% of pulse width increase at 900 nm per 1 m fiber). An ideal optical fiber endoscope needs to be several meters long and should enable both excitation and collection through the fiber. Therefore, we performed multiphoton imaging on endoscopy-compatible 1 m and 3 m lengths of fiber in the back-scattered geometry, wherein the signals were collected either directly (non-descanned detection) or through the fiber (descanned detection). Second harmonic images were collected from barium titanate crystals as well as from biological samples (mouse tail tendon). In non-descanned detection conditions, the ARFs outperformed the SCF by up to 10 times in terms of signal-to-noise ratio of images. Significantly, only the DC-ARF, due to its high numerical aperture (NA) of 0.45 and wide-collection bandwidth (>1 µm), could provide images in the de-scanned detection configuration desirable for endoscopy. Thus, our systematic characterization and comparison of different optical fibers under different image collection configurations, confirms and establishes the utility of DC-ARFs for high-performing label-free multiphoton imaging-based micro-endoscopy.

Magnetic position sensing for self-calibration and image registration of scanning fiber endoscopes

Magnetic position sensing for self-calibration and image registration of scanning fiber endoscopes

Iatrogenic Tracheal Rupture after Endotracheal Intubation: A Case Report

Iatrogenic tracheal rupture is very rare condition and has a lot off causes (intubation, tracheostomy, bronchoscopy, esophagectomy), but orotracheal intubation is the most common. Diagnosis is based on the occurrence of symptoms that are not specific but highly suggestive: subcutaneous emphysema, respiratory insufficiency, pneumothorax, and hemoptysis. The appearance of subcutaneous emphysema as a first sign plays a main role for early diagnosis and rapid appropriate treatment. Diagnostic confirmation is possible by chest X-ray, thoracic computed tomography and bronchoscopy which confirmed the size and site of the lesion. Treatment can be conservative, in patients with small ruptures, less than 2 cm, and surgical in the majority of ruptures over 2 cm in length.&#x0D; Our case report presents an iatrogenic post-intubation tracheal rupture treated conservatively. Our patient was a 71-year-old woman, admitted in our hospital with fracture of right humerus for elective surgery. Her medical history was only arterial hypertension. She underwent general anesthesia, intubated with flexible ET tube, positioned in beach-chair position after introduction, and no complication occurred during surgery. 18 hours after surgery, after severe coughing, she suddenly developed subcutaneous emphysema of the facial, neck and upper anterior chest. Tracheal rupture was confirmed with a thoracic computed tomography and tracheobronchial fiber endoscopy. It showed a posterior tracheal transmural rupture 1 cm long, located 4 cm above the carina, covered with small tissue that opened in inspirium. Conservative treatment with antibiotic cover was performed, and the patient was discharged home in good condition, fourteen days after the initial injury.

Multimode fiber endoscopes for computational brain imaging.

Advances in imaging tools have always been a pivotal driver for new discoveries in neuroscience. An ability to visualize neurons and subcellular structures deep within the brain of a freely behaving animal is integral to our understanding of the relationship between neural activity and higher cognitive functions. However, fast high-resolution imaging is limited to sub-surface brain regions and generally requires head fixation of the animal under the microscope. Developing new approaches to address these challenges is critical. The last decades have seen rapid progress in minimally invasive endo-microscopy techniques based on bare optical fibers. A single multimode fiber can be used to penetrate deep into the brain without causing significant damage to the overlying structures and provide high-resolution imaging. Here, we discuss how the full potential of high-speed super-resolution fiber endoscopy can be realized by a holistic approach that combines fiber optics, light shaping, and advanced computational algorithms. The recent progress opens up new avenues for minimally invasive deep brain studies in freely behaving mice.

Metaoptics for aberration correction in microendoscopy.

Compact and minimally invasive scanning fiber endoscopy probes with micron-level resolution have great potential in detailed tissue interrogation and early disease diagnosis, which are key applications of confocal reflectance imaging at visible wavelengths. State-of-the-art imaging probes commonly employ refractive lens triplets or gradient refractive index (GRIN) lenses as the micro-objective. However, off-axis aberration emerges as a critical factor affecting resolution, especially at the extremities of the imaging field. In response to this challenge, we propose what we believe to be a novel design integrating a metasurface with the GRIN micro-objective to address optical aberrations during beam scan. The metasurface acts as a corrector element for optical aberrations in a fiber-scanning endoscope using the same fiber for excitation and collection. Modeling such hybrid refractive-metasurface designs requires the coupling of simulation techniques across macroscale and nanoscale optics, for which we used an Ansys simulation workflow platform. Operating at a wavelength of 644 nm, this metaoptical element serves as a thin and compact aberration correction surface, ensuring uniform resolution across the entire imaging field. Experimental results from our scanning fiber endoscopy system demonstrate a notable enhancement in optical performance both on-axis and off-axis, achieving a resolution of 3 µm at the center of the imaging field. Impressively, the resolution experiences only a modest degradation by a factor of 0.13 at the edge of the field of view compared to the center.

Four-Photon Mixing in a Ghost Fiber Endoscope

Four-Photon Mixing in a Ghost Fiber Endoscope

Resolution-enhanced multi-core fiber imaging learned on a digital twin for cancer diagnosis.

Deep learning enables label-free all-optical biopsies and automated tissue classification. Endoscopic systems provide intraoperative diagnostics to deep tissue and speed up treatment without harmful tissue removal. However, conventional multi-core fiber (MCF) endoscopes suffer from low resolution and artifacts, which hinder tumor diagnostics. We introduce a method to enable unpixelated, high-resolution tumor imaging through a given MCF with a diameter of around 0.65mm and arbitrary core arrangement and inhomogeneous transmissivity. Image reconstruction is based on deep learning and the digital twin concept of the single-reference-based simulation with inhomogeneous optical properties of MCF and transfer learning on a small experimental dataset of biological tissue. The reference provided physical information about the MCF during the training processes. For the simulated data, hallucination caused by the MCF inhomogeneity was eliminated, and the averaged peak signal-to-noise ratio and structural similarity were increased from 11.2dB and 0.20 to 23.4dB and 0.74, respectively. By transfer learning, the metrics of independent test images experimentally acquired on glioblastoma tissue ex vivo can reach up to 31.6dB and 0.97 with 14fps computing speed. With the proposed approach, a single reference image was required in the pre-training stage and laborious acquisition of training data was bypassed. Validation on glioblastoma cryosections with transfer learning on only 50 image pairs showed the capability for high-resolution deep tissue retrieval and high clinical feasibility.

Calibration-free quantitative phase imaging in multi-core fiber endoscopes using end-to-end deep learning.

Quantitative phase imaging (QPI) through multi-core fibers (MCFs) has been an emerging in vivo label-free endoscopic imaging modality with minimal invasiveness. However, the computational demands of conventional iterative phase retrieval algorithms have limited their real-time imaging potential. We demonstrate a learning-based MCF phase imaging method that significantly reduced the phase reconstruction time to 5.5 ms, enabling video-rate imaging at 181 fps. Moreover, we introduce an innovative optical system that automatically generated the first, to the best of our knowledge, open-source dataset tailored for MCF phase imaging, comprising 50,176 paired speckles and phase images. Our trained deep neural network (DNN) demonstrates a robust phase reconstruction performance in experiments with a mean fidelity of up to 99.8%. Such an efficient fiber phase imaging approach can broaden the applications of QPI in hard-to-reach areas.

Method for automatically detecting light effect of comprehensive mirror body of medical fiber endoscope

Method for automatically detecting light effect of comprehensive mirror body of medical fiber endoscope

On the exploration of structured light transmission through a multimode fiber in a reference-less system

Recent advancements in optical wavefront shaping have brought multimode fibers (MMFs) into the spotlight as potential contenders for long-haul communication, positioning them as promising substitutes to single-mode fibers. MMFs offer greater data rates, countering the impending congestion of fiber-based networks. Additionally, their suitability for single fiber endoscope procedures presents them as compelling alternatives for minimally invasive endoscopy, providing information comparable to, if not surpassing, current cutting-edge technology. However, the complex modal behavior of light in MMFs hinders the implementation of these promising applications. Hence, precise modal excitation and control are crucial for improving the transmission of structured light in MMFs. This study introduces a groundbreaking approach that achieves the retrieval of the transmission matrix in a single step, thereby facilitating coherent light propagation through highly dispersive MMFs. By combining iterative phase retrieval algorithms with the measurement of phase shifts between experimentally established focal points, potential arbitrary interference control is enabled, leading to effective phase correction. The efficacy of our method is validated through the successful transmission of diverse structured light beams, including Laguerre–Gauss and Hermite–Gaussian types, as well as handwritten characters via MMF. The examination of structured light is simplified using an off-axis holographic technique that accurately captures both intensity and phase information. These results hold significant potential, paving the way for major advancements in long-distance communication and minimally invasive medical procedures, thereby transforming the telecommunications and healthcare sectors.

Successful treatment of post COVID-19 neurogenic dysphagia with botulinum toxin

Introduction: Dysphagia in post COVID-19 patients could be caused by several factors, including reduced pharyngolaryngeal coordination due to SARS-CoV-2 tropism to the central and/or peripheral nervous system. To our knowledge, this is the first reported case of COVID-19-related dysphagia successfully treated with botulinum toxin type A injection. Case description: We report the case of a patient with severe oropharyngeal dysphagia due to COVID-19 confirmed by fibre endoscopy. As a result, the patient required an enteral feeding tube. After two months of traditional swallowing therapies, there was only limited improvement. An electrophysiologic evaluation of the cricopharyngeal muscle was performed and showed a normal inhibition of the cricopharyngeal muscle, followed by a hypertonic rebound. Based on this result, we decided to perform a unilateral laryngeal injection of botulinum toxin type A. After the injection, the patient’s swallowing function improved significantly, allowing him to return to oral feeding. Discussion: Newly diagnosed oropharyngeal dysphagia was found in 35.3% of hospitalised patients with COVID-19. There are several possible causes of COVID-19-associated dysphagia, including stroke, encephalitis, critical illness neuropathy, Guillain-Barré syndrome and skeletal muscle injury. In our case, since stroke was excluded by brain MRI, cranial nerve injury was a possible explanation for the difficult recovery of swallowing despite daily swallowing therapy. Conclusion: We suggest that electrophysiology is a valid tool for the diagnosis and follow-up of patients with oropharyngeal dysphagia.

3D nanoprinting for fiber-integrated achromatic diffractive lens.

Achromatic performance is crucial for numerous multi-wavelength optical fiber applications, including endoscopic imaging and fiber sensing. This paper presents the design and nanoprinting of a fiber-integrated achromatic diffractive lens within the visible spectrum (450-650 nm). The 3D nanoprinting is achieved by a high-resolution direct laser writing technology, overcoming limitations in the optical performance caused by the lack of an arbitrary 3D structure writing capability and an insufficient feature resolution in the current manufacturing technology for visible light broadband achromatic diffractive lenses. A three-step optimization algorithm is proposed to effectively balance optical performance with writing difficulty. The characterization results demonstrate excellent achromatic focusing performance, paving the way towards the development of nanoprinted flat optical devices for applications such as optical fiber traps, miniature illumination systems, and integrated photonic chips.

Biomechanics of brain tissue damage caused by fiber endoscope penetration in third ventriculostomy surgery

Third ventriculostomy is the preferred treatment for obstructive hydrocephalus, but the biomechanics of brain tissue damage caused by fiber endoscopes remains unclear. In this study, brain tissue material parameters were tested based on the Ogden model to simulate needle puncture mechanics, and replicated the entire fiber endoscope advancement process during third ventriculostomy. It was found that a smaller diameter fiber endoscope, a perpendicular puncture angle, and a faster puncture speed would decrease the damage of brain tissue caused by the fiber endoscope. This study provides valuable insights for optimizing the instrumentation and surgical process of third ventriculostomy.

Iterative prototyping based on lessons learned from the falloposcope in vivo pilot study experience.

High grade serous ovarian cancer is the most deadly gynecological cancer, and it is now believed that most cases originate in the fallopian tubes (FTs). Early detection of ovarian cancer could double the 5-year survival rate compared with late-stage diagnosis. Autofluorescence imaging can detect serous-origin precancerous and cancerous lesions in ex vivo FT and ovaries with good sensitivity and specificity. Multispectral fluorescence imaging (MFI) can differentiate healthy, benign, and malignant ovarian and FT tissues. Optical coherence tomography (OCT) reveals subsurface microstructural information and can distinguish normal and cancerous structure in ovaries and FTs. We developed an FT endoscope, the falloposcope, as a method for detecting ovarian cancer with MFI and OCT. The falloposcope clinical prototype was tested in a pilot study with 12 volunteers to date to evaluate the safety and feasibility of FT imaging prior to standard of care salpingectomy in normal-risk volunteers. In this manuscript, we describe the multiple modifications made to the falloposcope to enhance robustness, usability, and image quality based on lessons learned in the clinical setting. The diameter falloposcope was introduced via a minimally invasive approach through a commercially available hysteroscope and introducing a catheter. A navigation video, MFI, and OCT of human FTs were obtained. Feedback from stakeholders on image quality and procedural difficulty was obtained. The falloposcope successfully obtained images in vivo. Considerable feedback was obtained, motivating iterative improvements, including accommodating the operating room environment, modifying the hysteroscope accessories, decreasing endoscope fragility and fiber breaks, optimizing software, improving fiber bundle images, decreasing gradient-index lens stray light, optimizing the proximal imaging system, and improving the illumination. The initial clinical prototype falloposcope was able to image the FTs, and iterative prototyping has increased its robustness, functionality, and ease of use for future trials.

Independently Actuated Soft Magnetic Manipulators for Bimanual Operations in Confined Anatomical Cavities

Soft magnetic manipulators offer the prospect of improved surgical outcomes through their potential for miniaturization and inherently safe tissue interaction. However, independent actuation of multiple manipulators within the same confined workspace is limited by undesired simultaneous actuation and manipulator–manipulator interactions. Herein, for the first time, approaches for the independent magnetic actuation of two magnetic continuum manipulators within the same confined workspace are proposed. A novel modular magnetic soft robot segment design is proposed with modified geometry to provide preferential bending planes and high angles of deflection. This design is integrated into two dual‐segment magnetic manipulators which, when arranged in parallel, can deliver independent bending in two planes of motion. Two distinct independent control strategies are proposed, based on orthogonal manipulator magnetization profiles and local field gradient control, respectively. Each dual‐manipulator configuration is characterized over a sequence of applied magnetic fields and gradients, induced via a dual robotically controlled external permanent magnet system. Manipulator independence, bending range of motion, and twisting behaviors are evaluated as a function of control strategy and manipulator separation distance. To demonstrate the system's potential in clinical scenarios, a dual‐manipulator configuration is adapted to carry an endoscopic camera and optic fiber, respectively. The resultant bimanual system is deployed in the confined anatomy of a skull‐base phantom to simulate minimally invasive ablation of a pituitary adenoma. Independent motion of the camera and tool within the confined workspace demonstrate the potential for an independent magnetic tool manipulation for surgical applications.