Comprehensive imaging of gastroesophageal biopsy samples by spectrally encoded confocal microscopy

Spectrally encoded dual-mode interferometry with orthogonal scanning

Spectrally encoded confocal microscopy (SECM) is a high-speed reflectance confocal microscopy technique. Here, we present a method to integrate optical coherence tomography (OCT) and SECM for complementary imaging by adding orthogonal scanning to the SECM configuration. The co-registration of SECM and OCT is automatic, as all system components are shared in the same order, eliminating the need for additional optical alignment. The proposed multimode imaging system is compact and cost-effective while providing the benefits of imaging aiming and guidance. Furthermore, speckle noise can be suppressed by averaging the speckles generated by shifting the spectral-encoded field in the direction of dispersion. Using a near infrared (NIR) card and a biological sample, we demonstrated the capability of the proposed system by showing SECM imaging at depths of interest guided by the OCT in real time and speckle noise reduction. Interfaced multimodal imaging of SECM and OCT was implemented at a speed of approximately 7 frames/s using fast-switching technology and GPU processing.

Investigation of different wavelengths for scattering-based light sheet microscopy

Scattering-based light sheet microscopy (sLSM) is a microscopy technique that can visualize cellular morphologic details based on the scattering signal. While sLSM was previously shown to image animal tissues ex vivo at a cellular resolution, the wavelength used was chosen based on other in vivo microscopy technologies rather than through a comparison of the sLSM imaging performance between different wavelengths. In this paper, we report the development of a multi-wavelength sLSM setup that facilitates the investigation of different wavelengths for sLSM imaging. Preliminary results of imaging human anal tissues ex vivo showed that the sLSM setup allowed for comparisons of the cellular imaging performance at the same tissue location between different wavelengths. Both the quantitative analysis of the image contrast and the visual assessment by a pathologist showed that the imaging depth increased with wavelength, and the imaging depth increase was most notable around 600 nm. The preliminary results showed that the multi-wavelength sLSM setup could be useful in identifying the optimal wavelength for the specific tissue type.

Imaging the dynamics and microstructure of fibrin clot polymerization in cardiac surgical patients using spectrally encoded confocal microscopy

During cardiac surgery with cardiopulmonary bypass (CPB), altered hemostatic balance may disrupt fibrin assembly, predisposing patients to perioperative hemorrhage. We investigated the utility of a novel device termed spectrally-encoded confocal microscopy (SECM) for assessing fibrin clot polymerization following heparin and protamine administration in CPB patients. SECM is a novel, high-speed optical approach to visualize and quantify fibrin clot formation in three dimensions with high spatial resolution (1.0 μm) over a volumetric field-of-view (165 × 4000 × 36 μm). The measurement sensitivity of SECM was first determined using plasma samples from normal subjects spiked with heparin and protamine. Next, SECM was performed in plasma samples from patients on CPB to quantify the extent to which fibrin clot dynamics and microstructure were altered by CPB exposure. In spiked samples, prolonged fibrin time (4.4 ± 1.8 to 49.3 ± 16.8 min, p < 0.001) and diminished fibrin network density (0.079 ± 0.010 to 0.001 ± 0.002 A.U, p < 0.001) with increasing heparin concentration were reported by SECM. Furthermore, fibrin network density was not restored to baseline levels in protamine-treated samples. In CPB patients, SECM reported lower fibrin network density in protaminized samples (0.055 ± 0.01 A.U. [Arbitrary units]) vs baseline values (0.066 ± 0.009 A.U.) (p = 0.03) despite comparable fibrin time (baseline = 6.0 ± 1.3, protamine = 6.4 ± 1.6 min, p = 0.5). In these patients, additional metrics including fibrin heterogeneity, length and straightness were quantified. Note, SECM revealed that following protamine administration with CPB exposure, fibrin clots were more heterogeneous (baseline = 0.11 ± 0.02 A.U, protamine = 0.08 ± 0.01 A.U, p = 0.008) with straighter fibers (baseline = 0.918 ± 0.003A.U, protamine = 0.928 ± 0.0006A.U. p < 0.001). By providing the capability to rapidly visualize and quantify fibrin clot microstructure, SECM could furnish a new approach for assessing clot stability and hemostasis in cardiac surgical patients.

Scattering-Based Light-Sheet Microscopy for Rapid Cellular Imaging of Fresh Tissue

BACKGROUND AND OBJECTIVES

Light-sheet microscopy (LSM) is a novel imaging technology that has been used for imaging fluorescence contrast in basic life science research. In this paper, we have developed a scattering-based LSM (sLSM) for rapidly imaging the cellular morphology of fresh tissues without any exogenous fluorescent dyes.

STUDY DESIGN/MATERIALS AND METHODS

In the sLSM device, a thin light sheet with the central wavelength of 834 nm was incident on the tissue obliquely, 45° relative to the tissue surface. The detection optics was configured to map the light sheet-illuminated area onto a two-dimensional imaging sensor. The illumination numerical aperture (NA) was set as 0.0625, and the detection NA 0.3.

RESULTS

The sLSM device achieved a light sheet thickness of less than 6.7 µm over 284 µm along the illumination optical axis. The detection optics of the sLSM device had a resolution of 1.8 µm. The sLSM images of the swine kidney ex vivo visualized tubules with similar sizes and shapes to those observed in histopathologic images. The swine duodenum sLSM images revealed cell nuclei and villi architecture in superficial lesions and glands in deeper regions.

CONCLUSIONS

The preliminary results suggest that sLSM may have the potential for rapidly examining the freshly-excised tissue ex vivo or intact tissue in vivo at microscopic resolution. Further optimization and performance evaluation of the sLSM technology will be needed in the future. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Moxifloxacin based fluorescence imaging of intestinal goblet cells

Goblet cells (GCs) in the intestine are specialized epithelial cells that secrete mucins to form the protective mucous layer. GCs are important in maintaining intestinal homeostasis, and the alteration of GCs is observed in inflammatory bowel diseases (IBDs) and neoplastic lesions. In the Barrett's esophagus, the presence of GCs is used as a marker of specialized intestinal metaplasia. Various endomicroscopic imaging methods have been used for imaging intestinal GCs, but high-speed and high-contrast GC imaging has been still difficult. In this study, we developed a high-contrast endoscopic GC imaging method: fluorescence endomicroscopy using moxifloxacin as a GC labeling agent. Moxifloxacin based fluorescence imaging of GCs was verified by using two-photon microscopy (TPM) in the normal mouse colon. Label-free TPM, which could visualize GCs in a negative contrast, was used as the reference. High-speed GC imaging was demonstrated by using confocal microscopy and endomicroscopy in the normal mouse colon. Confocal microscopy was applied to dextran sulfate sodium (DSS) induced colitis mouse models for the detection of GC depletion. Moxifloxacin based GC imaging was demonstrated not only by 3D microscopies but also by wide-field fluorescence microscopy, and intestinal GCs in the superficial region were imaged. Moxifloxacin based endomicroscopy has a potential for the application to human subjects by using FDA approved moxifloxacin.

Understanding optical reflectance contrast for real-time characterization of epithelial precursor lesions

Detecting early-stage epithelial cancers and their precursor lesions are challenging as lesions could be subtle and focally or heterogeneously distributed over large mucosal areas. Optical coherence tomography (OCT) that enables wide-field imaging of subsurface microstructures in vivo is a promising screening tool for epithelial diseases. However, its diagnostic capability has not been fully appreciated since the optical reflectance contrast is poorly understood. We investigated the back-scattered intensities from clustered or packed nanometer scale intracellular scatterers using finite-difference time-domain method and 1-μm resolution form of OCT, and uncovered that there existed correlations between the reflectance contrasts and the ultrastructural clustering or packing states of these scatterers, which allows us to interpret the physiological state of the cells. Specifically, both polarized goblet cells and foveolar cells exhibited asymmetric reflectance contrast, but they could be differentiated by the optical intensity of the mucin cup due to the different ultrastructural make-ups of the mucin granules; keratinocytes could demonstrate varied cytoplasmic intensity and their cytoplasmic contrast was closely correlated with the packing state of keratin filaments. Further preliminary study demonstrated that these new understandings of OCT image contrast enables the characterization of precancerous lesions, which could complement the current morphology-based criteria in realizing "virtual histology" and would have a profound impact for the screening and surveillance of epithelial cancers.

Contrast of nuclei in stratified squamous epithelium in optical coherence tomography images at 800 nm

Imaging nuclei of keratinocytes in the stratified squamous epithelium has been a subject of intense research since nucleus associated cellular atypia is the key criteria for the screening and diagnosis of epithelial cancers and their precursors. However, keratinocyte nuclei have been reported to be either low scattering or high scattering, so that these inconsistent reports might have led to misinterpretations of optical images, and more importantly, hindered the establishment of optical diagnostic criteria. We disclose that they are generally low scattering in the core using Micro-optical coherence tomography (μOCT) of 1.28-μm axial resolution in vivo; those previously reported "high scattering" or "bright" signals from nuclei are likely from the nucleocytoplasmic boundary, and the low-scattering nuclear cores were missed possibly due to insufficient axial resolutions (~4μm). It is further demonstrated that the high scattering signals may be associated with flattening of nuclei and cytoplasmic glycogen accumulation, which are valuable cytologic hallmarks of cell maturation.

A miniaturized, tethered, spectrally-encoded confocal endomicroscopy capsule

BACKGROUND AND OBJECTIVE

The tethered spectrally-encoded confocal endomicroscopy (SECM) capsule is an imaging device that once swallowed by an unsedated patient can visualize cellular morphologic changes associated with gastrointestinal (GI) tract diseases in vivo. Recently, we demonstrated a tethered SECM capsule for counting esophageal eosinophils in patients with eosinophilic esophagitis (EoE) in vivo. Yet, the current tethered SECM capsule is far too long to be widely utilized for imaging pediatric patients, who constitute a major portion of the EoE patient population. In this paper, we present a new tethered SECM capsule that is 33% shorter, has an easier and repeatable fabrication process, and produces images with reduced speckle noise.

MATERIALS AND METHODS

The smaller SECM capsule utilized a miniature condenser to increase the fiber numerical aperture and reduce the capsule length. A custom 3D-printed holder was developed to enable easy and repeatable device fabrication. A dual-clad fiber (DCF) was used to reduce speckle noise.

RESULTS

The fabricated SECM capsule (length = 20 mm; diameter = 7 mm) had a similar size and shape to a pediatric dietary supplement pill. The new capsule achieved optical sectioning thickness of 13.2 μm with a small performance variation between devices of 1.7 μm. Confocal images of human esophagus obtained in vivo showed the capability of this new device to clearly resolve microstructural epithelial details with reduced speckle noise.

CONCLUSIONS

We expect that the smaller size and better image performance of this new SECM capsule will greatly facilitate the clinical adoption of this technology in pediatric patients and will enable more accurate assessment of EoE-suspected tissues. Lasers Surg. Med. 51:452-458, 2019. © 2019 Wiley Periodicals, Inc.

Low-cost, high-speed near infrared reflectance confocal microscope

We have developed a low-cost, near-infrared (NIR) reflectance confocal microscope (RCM) to overcome challenges in the imaging depth and speed found in our previously-reported smartphone confocal microscope. In the new NIR RCM device, we have used 840 nm superluminescent LED (sLED) to increase the tissue imaging depth and speed. A new confocal detection optics has been developed to maintain high lateral resolution even when a relatively large slit width was used. The material cost of the NIR RCM device was still low, ~$5,200. The lateral resolution was 1.1 µm and 1.3 µm along the vertical and horizontal directions, respectively. Axial resolution was measured as 11.2 µm. In vivo confocal images of human forearm skin obtained at the imaging speed of 203 frames/sec clearly visualized characteristic epidermal and dermal cellular features of the human skin.

Rapid tissue histology using multichannel confocal fluorescence microscopy with focus tracking

BACKGROUND

Simplified hematoxylin and eosin (H&E) staining followed by cryo-sectioning enables rapid identification of cancerous tissue within the procedure room during Mohs micrographic surgery. Yet, a faster evaluation method is desirable as the staining protocol requires physically sectioning of the tissue after freezing, which leads to prolonged sectioning time along with the frozen artifacts that may occur in frozen sectioning.

METHODS

We present a multichannel confocal microscopy system to rapidly evaluate cancerous tissue. Using the optical sectioning capability of the confocal microscope, optically sectioned images of the freshly excised mouse tissue were acquired and converted into images resembling H&E histology. To show details of the nuclei and structure of the tissue, we applied a newly developed rapid tissue staining method using Hoechst 33342 and Eosin-Y. Line scanning and stitching was performed to overcome the limited field of view of the confocal microscope. Unlike previous confocal systems requiring an additional mechanical device to tilt the sample and match the focus of the objective lens, we developed a focus tracking method to rapidly scan large sample area. The focus tracking provides an effective means of keeping the image of the thick tissue in focus without additional devices. We then evaluated the performance of the confocal microscope to obtain optically sectioned images in thick tissue by comparing fluorescence stained slide images. We also obtained the corresponding H&E histology image to assess the potential of the system as a diagnostic tool.

RESULTS

We successfully imaged freshly excised mouse organs including stomach, tumor, and heart within a few minutes using the developed multichannel confocal microscopy and the tissue staining method. Using the pseudocolor method, colors of the acquired confocal grayscale images are converted to furthermore resemble Hematoxylin and Eosin histology. Due to the focus tracking and the line scanning, optically sectioned images were obtained over the large field of view. Comparisons with H&E histology have shown that the confocal images can acquire large details such as the ventricle as well as small details such as muscle fibers and nuclei.

CONCLUSIONS

This study confirms the use of confocal fluorescence microscopy technique to acquire rapid pathology results using optical sectioning, line scanning and focus tracking. We anticipate that the presented method will enable intraoperative histology and significantly reduce stress on patients undergoing surgery requiring repeated histology examinations.

Clinical Translation of Tethered Confocal Microscopy Capsule for Unsedated Diagnosis of Eosinophilic Esophagitis

Esophagogastroduodenoscopy (EGD) is a widely used procedure, posing significant financial burden on both healthcare systems and patients. Moreover, EGD is time consuming, sometimes difficult to tolerate, and suffers from an imperfect diagnostic yield as the limited number of collected biopsies does not represent the whole organ. In this paper, we report on technological and clinical feasibility of a swallowable tethered endomicroscopy capsule, which is administered without sedation, to image large regions of esophageal and gastric mucosa at the cellular level. To demonstrate imaging capabilities, we conducted a human pilot study (n = 17) on Eosinophilic Esophagitis (EoE) patients and healthy volunteers from which representative cases are presented and discussed. Results indicate that, compared to endoscopic biopsy, unsedated tethered capsule endomicroscopy obtains orders of magnitude more cellular information while successfully resolving characteristic tissue microscopic features such as stratified squamous epithelium, lamina propria papillae, intraepithelial eosinophils, and gastric cardia and body/fundic mucosa epithelia. Based on the major import of whole organ, cellular-level microscopy to obviate sampling error and the clear cost and convenience advantages of unsedated procedure, we believe that this tool has the potential to become a simpler and more effective device for diagnosing and monitoring the therapeutic response of EoE and other esophageal diseases.

Large-area spectrally encoded confocal endomicroscopy of the human esophagus in vivo

BACKGROUND AND OBJECTIVE

Diagnosis of esophageal diseases is often hampered by sampling errors that are inherent in endoscopic biopsy, the standard of care. Spectrally encoded confocal microscopy (SECM) is a high-speed reflectance confocal endomicroscopy technology that has the potential to visualize cellular features from large regions of the esophagus, greatly decreasing the likelihood of sampling error. In this paper, we report results from a pilot clinical study imaging the human esophagus in vivo with a prototype SECM endoscopic probe.

MATERIALS AND METHODS

In this pilot clinical study, six patients undergoing esophagogastroduodenoscopy (EGD) for surveillance of Barrett's esophagus (BE) were imaged with the SECM endoscopic probe. The device had a diameter of 7 mm, a length of 2 m, and a rapid-exchange guide wire provision for esophageal placement. During EGD, the distal portion of the esophagus of each patient was sprayed with 2.5% acetic acid to enhance nuclear contrast. The SECM endoscopic probe was then introduced over the guide wire to the distal esophagus and large-area confocal images were obtained by helically scanning the optics within the SECM probe.

RESULTS

Large area confocal images of the distal esophagus (image length = 4.3-10 cm; image width = 2.2 cm) were rapidly acquired at a rate of ∼9 mm² /second, resulting in short procedural times (1.8-4 minutes). SECM enabled the visualization of clinically relevant architectural and cellular features of the proximal stomach and normal and diseased esophagus, including squamous cell nuclei, BE glands, and goblet cells.

CONCLUSIONS

This study demonstrates that comprehensive spectrally encoded confocal endomicroscopy is feasible and can be used to visualize architectural and cellular microscopic features from large segments of the distal esophagus at the gastroesophageal junction. By providing microscopic images that are less subject to sampling error, this technology may find utility in guiding biopsy and planning and assessing endoscopic therapy. Lasers Surg. Med. 49:233-239, 2017. © 2016 Wiley Periodicals, Inc.

Spectrally encoded confocal microscopy for diagnosing breast cancer in excision and margin specimens

A large percentage of breast cancer patients treated with breast conserving surgery need to undergo multiple surgeries due to positive margins found during post-operative margin assessment. Carcinomas could be removed completely during the initial surgery and additional surgery avoided if positive margins can be determined intraoperatively. Spectrally encoded confocal microscopy (SECM) is a high-speed reflectance confocal microscopy technology that has a potential to rapidly image the entire surgical margin at subcellular resolution and accurately determine margin status intraoperatively. In this study, in order to test the feasibility of using SECM for intraoperative margin assessment, we have evaluated the diagnostic accuracy of SECM for detecting various types of breast cancers. Forty-six surgically removed breast specimens were imaged with an SECM system. Side-by-side comparison between SECM and histologic images showed that SECM images can visualize key histomorphologic patterns of normal/benign and malignant breast tissues. Small (500 μm × 500 μm) spatially registered SECM and histologic images (n=124 for each) were diagnosed independently by three pathologists with expertise in breast pathology. Diagnostic accuracy of SECM for determining malignant tissues was high, average sensitivity of 0.91, specificity of 0.93, positive predictive value of 0.95, and negative predictive value of 0.87. Intra-observer agreement and inter-observer agreement for SECM were also high, 0.87 and 0.84, respectively. Results from this study suggest that SECM may be developed into an intraoperative margin assessment tool for guiding breast cancer excisions.

Reflectance confocal microscopy of red blood cells: simulation and experiment

Measuring the morphology of red blood cells is important for clinical diagnosis, providing valuable indications on a patient's health. In this work, we have simulated the appearance of normal red blood cells under a reflectance confocal microscope and discovered unique relations between the morphological parameters and the resulting characteristic interference patterns of the cell. The simulation results showed good agreement with in vitro reflectance confocal images of red blood cells, acquired using spectrally encoded flow cytometry that imaged the cells in a linear flow without artificial staining. By matching the simulated patterns to confocal images of the cells, this method could be used for measuring cell morphology in three dimensions and for studying their physiology.

Three-dimensional photoacoustic endoscopic imaging of the rabbit esophagus

We report photoacoustic and ultrasonic endoscopic images of two intact rabbit esophagi. To investigate the esophageal lumen structure and microvasculature, we performed in vivo and ex vivo imaging studies using a 3.8-mm diameter photoacoustic endoscope and correlated the images with histology. Several interesting anatomic structures were newly found in both the in vivo and ex vivo images, which demonstrates the potential clinical utility of this endoscopic imaging modality. In the ex vivo imaging experiment, we acquired high-resolution motion-artifact-free three-dimensional photoacoustic images of the vasculatures distributed in the walls of the esophagi and extending to the neighboring mediastinal regions. Blood vessels with apparent diameters as small as 190 μm were resolved. Moreover, by taking advantage of the dual-mode high-resolution photoacoustic and ultrasound endoscopy, we could better identify and characterize the anatomic structures of the esophageal lumen, such as the mucosal and submucosal layers in the esophageal wall, and an esophageal branch of the thoracic aorta. In this paper, we present the first photoacoustic images showing the vasculature of a vertebrate esophagus and discuss the potential clinical applications and future development of photoacoustic endoscopy.

Three-dimensional photoacoustic endoscopic imaging of the rabbit esophagus

We report photoacoustic and ultrasonic endoscopic images of two intact rabbit esophagi. To investigate the esophageal lumen structure and microvasculature, we performed in vivo and ex vivo imaging studies using a 3.8-mm diameter photoacoustic endoscope and correlated the images with histology. Several interesting anatomic structures were newly found in both the in vivo and ex vivo images, which demonstrates the potential clinical utility of this endoscopic imaging modality. In the ex vivo imaging experiment, we acquired high-resolution motion-artifact-free three-dimensional photoacoustic images of the vasculatures distributed in the walls of the esophagi and extending to the neighboring mediastinal regions. Blood vessels with apparent diameters as small as 190 μm were resolved. Moreover, by taking advantage of the dual-mode high-resolution photoacoustic and ultrasound endoscopy, we could better identify and characterize the anatomic structures of the esophageal lumen, such as the mucosal and submucosal layers in the esophageal wall, and an esophageal branch of the thoracic aorta. In this paper, we present the first photoacoustic images showing the vasculature of a vertebrate esophagus and discuss the potential clinical applications and future development of photoacoustic endoscopy.

Comprehensive confocal endomicroscopy of the esophagus in vivo

BACKGROUND AND STUDY AIMS

Biopsy sampling error can be a problem for the diagnosis of certain gastrointestinal tract diseases. Spectrally-encoded confocal microscopy (SECM) is a high-speed reflectance confocal microscopy technology that has the potential to overcome sampling error by imaging large regions of gastrointestinal tract tissues. The aim of this study was to test a recently developed SECM endoscopic probe for comprehensively imaging large segments of the esophagus at the microscopic level in vivo.

METHODS

Topical acetic acid was endoscopically applied to the esophagus of a normal living swine. The 7 mm diameter SECM endoscopic probe was transorally introduced into the esophagus over a wire. Optics within the SECM probe were helically scanned over a 5 cm length of the esophagus. Confocal microscopy data was displayed and stored in real time.

RESULTS

Very large confocal microscopy images (length = 5 cm; circumference = 2.2 cm) of swine esophagus from three imaging depths, spanning a total area of 33 cm(2), were obtained in about 2 minutes. SECM images enabled the visualization of cellular morphology of the swine esophagus, including stratified squamous cell nuclei, basal cells, and collagen within the lamina propria.

CONCLUSIONS

The results from this study suggest that the SECM technology can rapidly provide large, contiguous confocal microscopy images of the esophagus in vivo. When applied to human subjects, the unique comprehensive, microscopic imaging capabilities of this technology may be utilized for improving the screening and surveillance of various esophageal diseases.

Miniature forward-viewing spectrally encoded endoscopic probe

Spectrally encoded endoscopy is a promising technique for minimally invasive imaging, allowing high-quality imaging through small diameter probes that do not require rapid mechanical scanning. A novel optical configuration that employs broadband visible light and dual-channel imaging is used to demonstrate a miniature forward-viewing probe having a high number of resolvable points, low speckle contrast, negligible backreflections, and high signal-to-noise ratio. The system would be most suitable for imaging through narrow ducts and vessels for clinical diagnosis at hard-to-reach locations in the body.

Tethered confocal endomicroscopy capsule for diagnosis and monitoring of eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is an allergic condition that is characterized by eosinophils infiltrating the esophageal wall. The treatment of the disease may require multiple follow up sedated endoscopies and biopsies to confirm elimination of eosinophils. These procedures are expensive, time consuming, and may be difficult for patients to tolerate. Here we report on the development of a confocal microscopy capsule for diagnosis and monitoring of EoE. The swallowable capsule implements a high-speed fiber-based reflectance confocal microscopy technique termed Spectrally Encoded Confocal Microscopy (SECM). SECM scans the sample in one dimension without moving parts by using wavelength swept source illumination and a diffraction grating at the back plane of the objective lens. As the wavelength of the source is tuned, the SECM optics within the 7 x 30 mm capsule are rotated using a driveshaft enclosed in a 0.8 mm flexible tether. A single rotation of the optics covered a field of view of 22 mm x 223 µm. The lateral and axial resolutions of the device were measured to be 2.1 and 14 µm, respectively. Images of Acetic Acid stained swine esophagus obtained with the capsule ex vivo and in vivo clearly showed squamous epithelial nuclei, which are smaller and less reflective than eosinophils. Imaging of esophageal biopsies from EoE patients ex vivo demonstrated the capability of this technology to visualize individual eosinophils. Based on the results of this study, we believe that this capsule will be a simpler and more effective device for diagnosing EoE and monitoring the therapeutic response of this disease.

New concepts in vocal fold imaging: a review

OBJECTIVE

To review new imaging technology potentially useful in the clinical practice of laryngology.

HYPOTHESIS

Narrow band imaging, iScan (Pentax Medical Company, Montvale, NJ), optical computed tomography, and confocal microscopy have potential value for enhancing diagnosis of laryngeal pathology.

DESIGN

Literature review.

METHODS

Literature search of computer databases including MEDLINE and PubMed.

RESULTS

A review of 50 articles suggests that new imaging technologies may enhance clinical diagnostic capabilities.

CONCLUSION

The probable value of new imaging technologies suggests that further research is needed to refine these technologies and define their clinical efficacy.

Endomicroscopy in Barrett's esophagus

Barrett's esophagus has been a focus of confocal laser endomicroscopy (CLE) research. There are two CLE systems available, one probe-based and the other with a microscope embedded in the tip of an endoscope. Several CLE image classification systems are available. Studies suggest that CLE has good sensitivity, negative predictive value, and accuracy for detecting neoplasia, with good interobserver agreement using the CLE image classification systems. Larger, multicenter studies have been completed evaluating the impact of CLE on treatment of patients with BE. Future developments may include more specific contrast agents and new types of endomicroscopes.

Confocal microscopy with strip mosaicing for rapid imaging over large areas of excised tissue

Confocal mosaicing microscopy is a developing technology platform for imaging tumor margins directly in freshly excised tissue, without the processing required for conventional pathology. Previously, mosaicing on 12-×-12  mm² of excised skin tissue from Mohs surgery and detection of basal cell carcinoma margins was demonstrated in 9 min. Last year, we reported the feasibility of a faster approach called "strip mosaicing," which was demonstrated on a 10-×-10  mm² of tissue in 3 min. Here we describe further advances in instrumentation, software, and speed. A mechanism was also developed to flatten tissue in order to enable consistent and repeatable acquisition of images over large areas. We demonstrate mosaicing on 10-×-10  mm² of skin tissue with 1-μm lateral resolution in 90 s. A 2.5-×-3.5  cm² piece of breast tissue was scanned with 0.8-μm lateral resolution in 13 min. Rapid mosaicing of confocal images on large areas of fresh tissue potentially offers a means to perform pathology at the bedside. Imaging of tumor margins with strip mosaicing confocal microscopy may serve as an adjunct to conventional (frozen or fixed) pathology for guiding surgery.

Spectrally encoded confocal microscopy of esophageal tissues at 100 kHz line rate

Spectrally encoded confocal microscopy (SECM) is a reflectance confocal microscopy technology that uses a diffraction grating to illuminate different locations on the sample with distinct wavelengths. SECM can obtain line images without any beam scanning devices, which opens up the possibility of high-speed imaging with relatively simple probe optics. This feature makes SECM a promising technology for rapid endoscopic imaging of internal organs, such as the esophagus, at microscopic resolution. SECM imaging of the esophagus has been previously demonstrated at relatively low line rates (5 kHz). In this paper, we demonstrate SECM imaging of large regions of esophageal tissues at a high line imaging rate of 100 kHz. The SECM system comprises a wavelength-swept source with a fast sweep rate (100 kHz), high output power (80 mW), and a detector unit with a large bandwidth (100 MHz). The sensitivity of the 100-kHz SECM system was measured to be 60 dB and the transverse resolution was 1.6 µm. Excised swine and human esophageal tissues were imaged with the 100-kHz SECM system at a rate of 6.6 mm(2)/sec. Architectural and cellular features of esophageal tissues could be clearly visualized in the SECM images, including papillae, glands, and nuclei. These results demonstrate that large-area SECM imaging of esophageal tissues can be successfully conducted at a high line imaging rate of 100 kHz, which will enable whole-organ SECM imaging in vivo.

Endoscopic probe optics for spectrally encoded confocal microscopy

Spectrally encoded confocal microscopy (SECM) is a form of reflectance confocal microscopy that can achieve high imaging speeds using relatively simple probe optics. Previously, the feasibility of conducting large-area SECM imaging of the esophagus in bench top setups has been demonstrated. Challenges remain, however, in translating SECM into a clinically-useable device; the tissue imaging performance should be improved, and the probe size needs to be significantly reduced so that it can fit into luminal organs of interest. In this paper, we report the development of new SECM endoscopic probe optics that addresses these challenges. A custom water-immersion aspheric singlet (NA = 0.5) was developed and used as the objective lens. The water-immersion condition was used to reduce the spherical aberrations and specular reflection from the tissue surface, which enables cellular imaging of the tissue deep below the surface. A custom collimation lens and a small-size grating were used along with the custom aspheric singlet to reduce the probe size. A dual-clad fiber was used to provide both the single- and multi- mode detection modes. The SECM probe optics was made to be 5.85 mm in diameter and 30 mm in length, which is small enough for safe and comfortable endoscopic imaging of the gastrointestinal tract. The lateral resolution was 1.8 and 2.3 µm for the single- and multi- mode detection modes, respectively, and the axial resolution 11 and 17 µm. SECM images of the swine esophageal tissue demonstrated the capability of this device to enable the visualization of characteristic cellular structural features, including basal cell nuclei and papillae, down to the imaging depth of 260 µm. These results suggest that the new SECM endoscopic probe optics will be useful for imaging large areas of the esophagus at the cellular scale in vivo.

Optical endomicroscopy and the road to real-time, in vivo pathology: present and future

Epithelial cancers account for substantial mortality and are an important public health concern. With the need for earlier detection and treatment of these malignancies, the ability to accurately detect precancerous lesions has an increasingly important role in controlling cancer incidence and mortality. New optical technologies are capable of identifying early pathology in tissues or organs in which cancer is known to develop through stages of dysplasia, including the esophagus, colon, pancreas, liver, bladder, and cervix. These diagnostic imaging advances, together as a field known as optical endomicroscopy, are based on confocal microscopy, spectroscopy-based imaging, and optical coherence tomography (OCT), and function as "optical biopsies," enabling tissue pathology to be imaged in situ and in real time without the need to excise and process specimens as in conventional biopsy and histopathology. Optical biopsy techniques can acquire high-resolution, cross-sectional images of tissue structure on the micron scale through the use of endoscopes, catheters, laparoscopes, and needles. Since the inception of these technologies, dramatic technological advances in accuracy, speed, and functionality have been realized. The current paradigm of optical biopsy, or single-area, point-based images, is slowly shifting to more comprehensive microscopy of larger tracts of mucosa. With the development of Fourier-domain OCT, also known as optical frequency domain imaging or, more recently, volumetric laser endomicroscopy, comprehensive surveillance of the entire distal esophagus is now achievable at speeds that were not possible with conventional OCT technologies. Optical diagnostic technologies are emerging as clinically useful tools with the potential to set a new standard for real-time diagnosis. New imaging techniques enable visualization of high-resolution, cross-sectional images and offer the opportunity to guide biopsy, allowing maximal diagnostic yields and appropriate staging without the limitations and risks inherent with current random biopsy protocols. However, the ability of these techniques to achieve widespread adoption in clinical practice depends on future research designed to improve accuracy and allow real-time data transmission and storage, thereby linking pathology to the treating physician. These imaging advances are expected to eventually offer a see-and-treat paradigm, leading to improved patient care and potential cost reduction.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/5372548637202968.

Dual-channel spectrally encoded endoscopic probe

High quality imaging through sub-millimeter endoscopic probes provides clinicians with valuable diagnostics capabilities in hard to reach locations within the body. Spectrally encoded endoscopy (SEE) has been shown promising for such task; however, challenging probe fabrication and high speckle noise had prevented its testing in in vivo studies. Here we demonstrate a novel miniature SEE probe which incorporates some of the recent progress in spectrally encoded technology into a compact and robust endoscopic system. A high-quality miniature diffraction grating was fabricated using automated femtosecond laser cutting from a large bulk grating. Using one spectrally encoded channel for imaging and a separate channel for incoherent illumination, the new system has large depth of field, negligible back reflections and well controlled speckle noise which depends on the core diameter of the illumination fiber. Moreover, by using a larger imaging channel, higher groove density grating, shorter wavelength and broader spectrum, the new endoscopic system now allow significant improvements in almost all imaging parameter compared to previous systems, through an ultra-miniature endoscopic probe.

Noninvasive imaging of flowing blood cells using label-free spectrally encoded flow cytometry

Optical microscopy of blood cells in vivo provides a unique opportunity for clinicians and researchers to visualize the morphology and dynamics of circulating cells, but is usually limited by the imaging speed and by the need for exogenous labeling of the cells. Here we present a label-free approach for in vivo flow cytometry of blood using a compact imaging probe that could be adapted for bedside real-time imaging of patients in clinical settings, and demonstrate subcellular resolution imaging of red and white blood cells flowing in the oral mucosa of a human volunteer. By analyzing the large data sets obtained by the system, valuable blood parameters could be extracted and used for direct, reliable assessment of patient physiology.

Endoscopic imaging of Cerenkov luminescence

We demonstrate feasibility of endoscopic imaging of Cerenkov light originated when charged nuclear particles, emitted from radionuclides, travel through a biological tissue of living subjects at superluminal velocity. The endoscopy imaging system consists of conventional optical fiber bundle/ clinical endoscopes, an optical imaging lens system, and a sensitive low-noise charge coupled device (CCD) camera. Our systematic studies using phantom samples show that Cerenkov light from as low as 1 µCi of radioactivity emitted from (18)F-Fluorodeoxyglucose (FDG) can be coupled and transmitted through conventional optical fibers and endoscopes. In vivo imaging experiments with tumor bearing mice, intravenously administered with (18)F-FDG, further demonstrated that Cerenkov luminescence endoscopy is a promising new tool in the field of endoscopic molecular imaging.

Imaging inflammation in mouse colon using a rapid stage-scanning confocal fluorescence microscope

Large area confocal microscopy may provide fast, high-resolution image acquisition for evaluation of tissue in pre-clinical studies with reduced tissue processing in comparison to histology. We present a rapid beam and stage-scanning confocal fluorescence microscope to image cellular and tissue features along the length of the entire excised mouse colon. The beam is scanned at 8,333 lines/sec by a polygon scanning mirror while the specimen is scanned in the orthogonal axis by a motorized translation stage with a maximum speed of 7 mm/sec. A single 1 × 60 mm(2) field of view image spanning the length of the mouse colon is acquired in 10 s. Z-projection images generated from axial image stacks allow high resolution imaging of the surface of non-flat specimens. In contrast to the uniform size, shape, and distribution of colon crypts in confocal images of normal colon, confocal images of chronic bowel inflammation exhibit heterogeneous tissue structure with localized severe crypt distortion.

Reflectance confocal microscopy for the diagnosis of eosinophilic esophagitis: a pilot study conducted on biopsy specimens

BACKGROUND

Diagnosis of eosinophilic esophagitis (EoE) currently requires endoscopic biopsy and histopathologic analysis of the biopsy specimens to count intraepithelial eosinophils. Reflectance confocal microscopy (RCM) is an endomicroscopy technology that is capable of obtaining high-resolution, optically sectioned images of esophageal mucosa without the administration of exogenous contrast.

OBJECTIVE

In this study, we investigated the capability of a high-speed form of RCM, termed spectrally encoded confocal microscopy (SECM), to count intraepithelial esophageal eosinophils and characterize other microscopic findings of EoE.

DESIGN

A total of 43 biopsy samples from 35 pediatric patients and 8 biopsy samples from 8 adult patients undergoing EGD for EoE were imaged by SECM immediately after their removal and then processed for routine histopathology. Two SECM readers, trained on adult cases, prospectively counted intraepithelial eosinophils and detected the presence of abscess, degranulation, and basal cell hyperplasia on SECM images from the pediatric patients. A pathologist blinded to the SECM data analyzed the same from corresponding slides.

SETTING

The Gastrointestinal Unit, Massachusetts General Hospital.

RESULTS

Eosinophils by SECM demonstrated a higher reflectance than the surrounding cells and other inflammatory cells. There was good correlation between SECM and histology maximum eosinophil counts/high-power field (R = 0.76, P < .0001). Intra- and interobserver correlations for SECM counts were very good (R = 0.93 and R = 0.92, respectively; P < .0001). For the commonly used eosinophil count cutoff of 15 per high-power field, the sensitivity and specificity of SECM for EoE were 100%. The sensitivity and specificity for abscess, degranulation, and basal cell hyperplasia were 100% and 82%, 91% and 60%, and 94% and 80%, respectively. Intra- and interobserver agreements for these microscopic features of EoE were very good (κ = 0.9/0.9, 0.84/1.0, 0.91/0.81, respectively).

LIMITATION

Ex vivo study.

CONCLUSIONS

This study demonstrates that RCM can be used to accurately count intraepithelial eosinophils and identify other microscopic abnormalities associated with EoE on freshly excised biopsy samples. These findings suggest that RCM may be developed into a tool for assessing eosinophilic infiltration in the esophagus in vivo.

Endomicroscopy in the evaluation of Barrett's esophagus

PURPOSE OF REVIEW

Confocal laser endomicroscopy (CLE) can provide real-time, microscopic visualization of the gastrointestinal mucosa, allowing an endoscopic approach to the histologic evaluation of Barrett's esophagus and Barrett's esophagus-associated neoplasia.

RECENT FINDINGS

Both endoscope-based (eCLE) and probe-based (pCLE) CLE systems have been used to evaluate Barrett's esophagus and Barrett's esophagus-associated neoplasia. Criteria for distinguishing Barrett's esophagus with neoplasia from nondysplastic Barrett's esophagus have been developed and validated for both eCLE and pCLE. Several studies have shown excellent detection of Barrett's esophagus neoplasia by CLE, and the technique may be used to guide endoscopic therapy. Advanced endomicroscopy systems and peptides and antibodies that target neoplasia are in development.

SUMMARY

CLE has provided a new way of evaluating Barrett's esophagus and Barrett's esophagus-associated neoplasia and is being used to improve detection and management of neoplasia in Barrett's esophagus.

Comprehensive volumetric confocal microscopy with adaptive focusing

Comprehensive microscopy of distal esophagus could greatly improve the screening and surveillance of esophageal diseases such as Barrett's esophagus by providing histomorphologic information over the entire region at risk. Spectrally encoded confocal microscopy (SECM) is a high-speed reflectance confocal microscopy technology that can be configured to image the entire distal esophagus by helically scanning the beam using optics within a balloon-centering probe. It is challenging to image the human esophagus in vivo with balloon-based SECM, however, because patient motion and anatomic tissue surface irregularities decenter the optics, making it difficult to keep the focus at a predetermined location within the tissue as the beam is scanned. In this paper, we present a SECM probe equipped with an adaptive focusing mechanism that can compensate for tissue surface irregularity and dynamic focal variation. A tilted arrangement of the objective lens is employed in the SECM probe to provide feedback signals to an adaptive focusing mechanism. The tilted configuration also allows the probe to obtain reflectance confocal data from multiple depth levels, enabling the acquisition of three-dimensional volumetric data during a single scan of the probe. A tissue phantom with a surface area of 12.6 cm(2) was imaged using the new SECM probe, and 8 large-area reflectance confocal microscopy images were acquired over the depth range of 56 μm in 20 minutes. Large-area SECM images of excised swine small intestine tissue were also acquired, enabling the visualization of villous architecture, epithelium, and lamina propria. The adaptive focusing mechanism was demonstrated to enable acquisition of in-focus images even when the probe was not centered and the tissue surface was irregular.

Endomicroscopy of Barrett's Esophagus

Endomicroscopy is a remarkable technical advance in gastrointestinal mucosa imaging. In 2003, Kiesslich and colleagues described the first human use of contrast-aided confocal laser endomicroscopy (CLE) as a novel technique for in vivo microscopic imaging of the gastrointestinal mucosa. Both probe-based and endoscope-based systems have been applied to many gastrointestinal disorders, including Barrett's esophagus (BE) and associated neoplasia. Probe-based confocal laser endomicroscopy can be used in conjunction with highresolution white light endoscopy and other contrast enhancement techniques. It has proven high accuracy for prediction of high-grade neoplasia and cancer. In vivo imaging of both flat BE and mucosal lesions can influence diagnosis and thereby impact upon decision making regarding tissue sampling and endoscopic therapy. This article discusses the scientific literature related to clinical use of CLE for BE, the techniques for performing CLE in the esophagus, and the potential future directions for CLE in BE and esophageal cancer diagnosis and treatment.