Diagnostic performance of two confocal endomicroscopy systems in detecting Barrett's dysplasia: a pilot study using a novel bioprobe in ex vivo tissue

Development of Advanced Imaging and Molecular Imaging for Barrett's Neoplasia

Barrett esophagus (BE) is a precursor to a life-threatening esophageal adenocarcinoma (EAC). Surveillance endoscopy with random biopsies is recommended for early intervention against EAC, but its adherence in the clinical setting is poor. Dysplastic lesions with flat architecture and patchy distribution in BE are hardly detected by high-resolution endoscopy, and the surveillance protocol entails issues of time and labor and suboptimal interobserver agreement for diagnosing dysplasia. Therefore, the development of advanced imaging technologies is necessary for Barrett's surveillance. Recently, non-endoscopic or endoscopic technologies, such as cytosponge, endocytoscopy, confocal laser endomicroscopy, autofluorescence imaging, and optical coherence tomography/volumetric laser endomicroscopy, were developed, but most of them are not clinically available due to the limited view field, expense of the equipment, and significant time for the learning curve. Another strategy is focused on the development of molecular biomarkers, which are also not ready to use. However, a combination of advanced imaging techniques together with specific biomarkers is expected to identify morphological abnormalities and biological disorders at an early stage in the surveillance. Here, we review recent developments in advanced imaging and molecular imaging for Barrett's neoplasia. Further developments in multiple biomarker panels specific for Barrett's HGD/EAC include wide-field imaging systems for targeting 'red flags', a high-resolution imaging system for optical biopsy, and a computer-aided diagnosis system with artificial intelligence, all of which enable a real-time and accurate diagnosis of dysplastic BE in Barrett's surveillance and provide information for precision medicine.

A guide to multimodal endoscopy imaging for gastrointestinal malignancy - an early indicator

Multimodality imaging is an essential aspect of endoscopic surveillance for the detection of neoplastic lesions, such as dysplasia or intramucosal cancer, because it improves the efficacy of endoscopic surveillance and therapeutic procedures in the gastrointestinal tract. This approach reveals mucosal abnormalities that cannot be detected by standard endoscopy. Currently, these imaging techniques are divided into those for primary detection and those for targeted imaging and characterization, the latter being used to visualize areas of interest in detail and permit histological evaluation. This Review outlines the use of virtual chromoendoscopy, narrow-band imaging, autofluorescence imaging, optical coherence tomography, confocal endomicroscopy and volumetric laser endomicroscopy as new imaging techniques for diagnostic investigation of the gastrointestinal tract. Insights into use of multimodal endoscopic imaging for early disease detection, in particular for pre-malignant lesions, in the oesophagus, stomach and colon are described.

Ex Vivo (Fluorescence) Confocal Microscopy in Surgical Pathology: State of the Art

First developed in 1957, confocal microscopy is a powerful imaging tool that can be used to obtain near real-time reflected light images of untreated human tissue with nearly histologic resolution. Besides its research applications, in the last decades, confocal microscopy technology has been proposed as a useful device to improve clinical diagnosis, especially in ophthalmology, dermatology, and endomicroscopy settings, thanks to advances in instrument development. Compared with the wider use of the in vivo tissue assessment, ex vivo applications of confocal microscopy are not fully explored. A comprehensive review of the current literature was performed here, focusing on the reliable applications of ex vivo confocal microscopy in surgical pathology and on some potential evolutions of this new technique from pathologists' viewpoint.

Comparative diagnostic performance of volumetric laser endomicroscopy and confocal laser endomicroscopy in the detection of dysplasia associated with Barrett's esophagus

BACKGROUND AND AIMS

Probe-based confocal laser endomicroscopy (pCLE) and volumetric laser endomicroscopy (VLE) (also known as frequency domain optical coherence tomography) are advanced endoscopic imaging modalities that may be useful in the diagnosis of dysplasia associated with Barrett's esophagus (BE). We performed pCLE examination in ex-vivo EMR specimens and compared the diagnostic performance of using the current VLE scoring index (previously established as OCT-SI) and a novel VLE diagnostic algorithm (VLE-DA) for the detection of dysplasia.

METHODS

A total of 27 patients with BE enrolled in a surveillance program at a tertiary-care center underwent 50 clinically indicated EMRs that were imaged with VLE and pCLE and classified into neoplastic (N = 34; high-grade dysplasia, intramucosal adenocarcinoma) and nonneoplastic (N = 16; low-grade dysplasia, nondysplastic BE), based on histology. Image datasets (VLE, N = 50; pCLE, N = 50) were rated by 3 gastroenterologists trained in the established diagnostic criteria for each imaging modality as well as a new diagnostic algorithm for VLE derived from a training set that demonstrated association of specific VLE features with neoplasia. Sensitivity, specificity, and diagnostic accuracy were assessed for each imaging modality and diagnostic criteria.

RESULTS

The sensitivity, specificity, and diagnostic accuracy of pCLE for detection of BE dysplasia was 76% (95% confidence interval [CI], 59-88), 79% (95% CI, 53-92), and 77% (95% CI, 72-82), respectively. The optimal diagnostic performance of OCT-SI showed a sensitivity of 70% (95% CI, 52-84), specificity of 60% (95% CI, 36-79), and diagnostic accuracy of 67%; (95% CI, 58-78). The use of the novel VLE-DA showed a sensitivity of 86% (95% CI, 69-96), specificity of 88% (95% CI, 60-99), and diagnostic accuracy of 87% (95% CI, 86-88). The diagnostic accuracy of using the new VLE-DA criteria was significantly superior to the current OCT-SI (P < .01).

CONCLUSION

The use of a new VLE-DA showed enhanced diagnostic performance for detecting BE dysplasia ex vivo compared with the current OCT-SI. Further validation of this algorithm in vivo is warranted.

Imaging hamster model of bile duct cancer in vivo using fluorescent L-glucose derivatives

Extrahepatic bile duct cancer (cholangiocarcinoma) has a poor prognosis. Since surgical resection is the only way to prolong the patient’s life, it is of critical importance to correctly determine the extent of lesions. However, conventional pre-operative assessments have insufficient spatial resolution for determining the surgical margin. A fluorescent contrast agent might provide a more precise measure to identify anomalies in biliary surface, when combined with probe-based confocal laser endomicroscopy (pCLE). We have previously shown that 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxy-l-glucose (2-NBDLG), a fluorescent derivative of l-glucose (fLG), is specifically taken up into spheroids consisting of cells showing heterogeneous nuclear-cytoplasm ratio, a feature of malignant cells in clinical settings. In addition, a combined use of 2-TRLG, a membrane-impermeable fLG, with 2-NBDLG visualized membrane integrity as well. We therefore explored in the present study the availability of the fLGs in vivo as a contrast agent for pCLE by using a hamster model of cholangiocarcinoma. Extrahepatic cholangiocarcinoma developed in mid common duct in ~20 % of the animals subjected to cholecystoduodenostomy with the ligation at the distal end of the common duct followed by injection of a carcinogen N-nitrosobis(2-oxopropyl)amine. After infusing bile duct with a solution containing 2-NBDLG and 2-TRLG, the lumen was surgically exposed and examined by pCLE. Fluorescence pattern characterized by bright spots and dark clumps was detected in the areas diagnosed with cholangiocarcinoma in later histopathology, whereas no such pattern was detected in control animals. These findings may form a basis for elucidating a potential availability of fLGs in imaging cholangiocarcinoma by pCLE.

Novel application of complementary imaging techniques to examine in vivo glucose metabolism in the kidney

The metabolic status of the kidney is a determinant of injury susceptibility and a measure of progression for many disease processes; however, noninvasive modalities to assess kidney metabolism are lacking. In this study, we employed positron emission tomography (PET) and intravital multiphoton microscopy (MPM) to assess cortical and proximal tubule glucose tracer uptake, respectively, following experimental perturbations of kidney metabolism. Applying dynamic image acquisition PET with 2-¹⁸fluoro-2-deoxyglucose (¹⁸F-FDG) and tracer kinetic modeling, we found that an intracellular compartment in the cortex of the kidney could be distinguished from the blood and urine compartments in animals. Given emerging literature that the tumor suppressor protein p53 is an important regulator of cellular metabolism, we demonstrated that PET imaging was able to discern a threefold increase in cortical ¹⁸F-FDG uptake following the pharmacological inhibition of p53 in animals. Intravital MPM with the fluorescent glucose analog 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose (2-NBDG) provided increased resolution and corroborated these findings at the level of the proximal tubule. Extending our observation of p53 inhibition on proximal tubule glucose tracer uptake, we demonstrated by intravital MPM that pharmacological inhibition of p53 diminishes mitochondrial potential difference. We provide additional evidence that inhibition of p53 alters key metabolic enzymes regulating glycolysis and increases intermediates of glycolysis. In summary, we provide evidence that PET is a valuable tool for examining kidney metabolism in preclinical and clinical studies, intravital MPM is a powerful adjunct to PET in preclinical studies of metabolism, and p53 inhibition alters basal kidney metabolism.

Comparison between two types of confocal laser endomicroscopy in gastrointestinal tract

OBJECTIVES

Confocal laser endomicroscopy (CLE) consists of endoscope-based CLE (eCLE) and probe-based CLE (pCLE). This study aimed to compare eCLE and pCLE in their diagnostic yield in different parts of the gastrointestinal (GI) tract.

METHODS

Consecutive patients were scheduled for CLE examination due to GI symptoms. All patients were randomly assigned to eCLE or pCLE group and underwent a programmed procedure using one type of CLE. Differences in procedure time, complication rate, CLE image quality and image acquisition feasibility between these two types of CLE for esophagogastroduodenoscopy (EGD) and colonoscopy were calculated.

RESULTS

Altogether 513 CLE procedures were performed, including 324 EGD and 189 colonoscopy. The procedure time of pCLE was significantly shorter than that of eCLE both in EGD and colonoscopy (16.78 min vs 18.13 min for EGD, P = 0.027; 32.48 min vs 39.89 min for colonoscopy, P < 0.001). No significant difference was found between these two types of CLE in diagnostic utility, including the detection and prediction of histopathological results of the lesions. The CLE image quality of both eCLE and pCLE were comparable in the stomach and colon, but eCLE seemed to be superior to pCLE in examining the esophagus. Colonoscopy using pCLE had a higher complete rate than that of eCLE, although the difference was not statistically significant (P = 0.065).

CONCLUSIONS

pCLE is more flexible in diagnosing GI diseases with a shorter procedure time than eCLE regardless of comparable diagnostic yields, except the diagnosis of esophageal diseases in which eCLE provides better image quality.

Emerging enhanced imaging technologies of the esophagus: spectroscopy, confocal laser endomicroscopy, and optical coherence tomography

BACKGROUND

Despite advances in diagnoses and therapy, esophageal adenocarcinoma remains a highly lethal neoplasm. Hence, a great interest has been placed in detecting early lesions and in the detection of Barrett esophagus (BE). Advanced imaging technologies of the esophagus have then been developed with the aim of improving biopsy sensitivity and detection of preplastic and neoplastic cells. The purpose of this article was to review emerging imaging technologies for esophageal pathology, spectroscopy, confocal laser endomicroscopy (CLE), and optical coherence tomography (OCT).

METHODS

We conducted a PubMed search using the search string "esophagus or esophageal or oesophageal or oesophagus" and "Barrett or esophageal neoplasm" and "spectroscopy or optical spectroscopy" and "confocal laser endomicroscopy" and "confocal microscopy" and "optical coherence tomography." The first and senior author separately reviewed all articles. Our search identified: 19 in vivo studies with spectroscopy that accounted for 1021 patients and 4 ex vivo studies; 14 clinical CLE in vivo studies that accounted for 941 patients and 1 ex vivo study with 13 patients; and 17 clinical OCT in vivo studies that accounted for 773 patients and 2 ex vivo studies.

RESULTS

Human studies using spectroscopy had a very high sensitivity and specificity for the detection of BE. CLE showed a high interobserver agreement in diagnosing esophageal pathology and an accuracy of predicting neoplasia. We also found several clinical studies that reported excellent diagnostic sensitivity and specificity for the detection of BE using OCT.

CONCLUSIONS

Advanced imaging technology for the detection of esophageal lesions is a promising field that aims to improve the detection of early esophageal lesions. Although advancing imaging techniques improve diagnostic sensitivities and specificities, their integration into diagnostic protocols has yet to be perfected.

Molecular confocal laser endomicroscopy: A novel technique for in vivo cellular characterization of gastrointestinal lesions

While flexible endoscopy is essential for macroscopic evaluation, confocal laser endomicroscopy (CLE) has recently emerged as an endoscopic method enabling visualization at a cellular level. Two systems are currently available, one based on miniprobes that can be inserted via a conventional endoscope or via a needle guided by endoscopic ultrasound. The second system has a confocal microscope integrated into the distal part of an endoscope. By adding molecular probes like fluorescein conjugated antibodies or fluorescent peptides to this procedure (either topically or systemically administered during on-going endoscopy), a novel world of molecular evaluation opens up. The method of molecular CLE could potentially be used for estimating the expression of important receptors in carcinomas, subsequently resulting in immediate individualization of treatment regimens, but also for improving the diagnostic accuracy of endoscopic procedures by identifying otherwise invisible mucosal lesions. Furthermore, studies have shown that fluorescein labelled drugs can be used to estimate the affinity of the drug to a target organ, which probably can be correlated to the efficacy of the drug. However, several of the studies in this research field have been conducted in animal facilities or in vitro, while only a limited number of trials have actually been carried out in vivo. Therefore, safety issues still needs further evaluations. This review will present an overview of the implications and pitfalls, as well as future challenges of molecular CLE in gastrointestinal diseases.

Advanced imaging technologies for the detection of dysplasia and early cancer in barrett esophagus

Advanced esophageal adenocarcinomas arising from Barrett esophagus (BE) are tumors with an increasing incidence and poor prognosis. The aim of endoscopic surveillance of BE is to detect dysplasia, particularly high-grade dysplasia and intramucosal cancers that can subsequently be treated endoscopically before progression to invasive cancer with lymph node metastases. Current surveillance practice standards require the collection of random 4-quadrant biopsy specimens over every 1 to 2 cm of BE (Seattle protocol) to detect dysplasia with the assistance of white light endoscopy, in addition to performing targeted biopsies of recognizable lesions. This approach is labor-intensive but should currently be considered state of the art. Chromoendoscopy, virtual chromoendoscopy (e.g., narrow band imaging), and confocal laser endomicroscopy, in addition to high-definition standard endoscopy, might increase the diagnostic yield for the detection of dysplastic lesions. Until these modalities have been demonstrated to enhance efficiency or cost effectiveness, the standard protocol will remain careful examination using conventional off the shelf high-resolution endoscopes, combined with as longer inspection time which is associated with increased detection of dysplasia.

Assessment of the diagnostic performance and interobserver variability of endocytoscopy in Barrett’s esophagus: A pilot ex-vivo study

AIM: To investigate a classification of endocytoscopy (ECS) images in Barrett’s esophagus (BE) and evaluate its diagnostic performance and interobserver variability.

METHODS: ECS was applied to surveillance endoscopic mucosal resection (EMR) specimens of BE ex-vivo. The mucosal surface of specimen was stained with 1% methylene blue and surveyed with a catheter-type endocytoscope. We selected still images that were most representative of the endoscopically suspect lesion and matched with the final histopathological diagnosis to accomplish accurate correlation. The diagnostic performance and inter-observer variability of the new classification scheme were assessed in a blinded fashion by physicians with expertise in both BE and ECS and inexperienced physicians with no prior exposure to ECS.

RESULTS: Three staff physicians and 22 gastroenterology fellows classified eight randomly assigned unknown still ECS pictures (two images per each classification) into one of four histopathologic categories as follows: (1) BEC1-squamous epithelium; (2) BEC2-BE without dysplasia; (3) BEC3-BE with dysplasia; and (4) BEC4-esophageal adenocarcinoma (EAC) in BE. Accuracy of diagnosis in staff physicians and clinical fellows were, respectively, 100% and 99.4% for BEC1, 95.8% and 83.0% for BEC2, 91.7% and 83.0% for BEC3, and 95.8% and 98.3% for BEC4. Interobserver agreement of the faculty physicians and fellows in classifying each category were 0.932 and 0.897, respectively.

CONCLUSION: This is the first study to investigate classification system of ECS in BE. This ex-vivo pilot study demonstrated acceptable diagnostic accuracy and excellent interobserver agreement.

Endoscopic mucosal imaging of gastrointestinal neoplasia in 2013

The holy grail of gastrointestinal endoscopy consists of the detection, in vivo characterization, and endoscopic removal of early or premalignant mucosal lesions. While our ability to achieve this goal has improved substantially since the development of the modern video-endoscope, inadequate visual inspection, errors of interpretation, and lesion subtlety all contribute to the continued suboptimal detection and assessment of early neoplasia. A myriad of new technologies has thus emerged that may help resolve these shortcomings; high magnification endoscopes, as well as the techniques of dye-based and virtual chromoendoscopy, are now widely available, while confocal laser endomicroscopy and endocystoscopy, optical coherence tomography, and autofluorescence imaging are generally applicable only in a research setting. Such technologies can be broadly categorized according to whether they potentially afford endoscopists improved detection, or real-time characterization, of mucosal lesions. Enhanced detection of otherwise "invisible" lesions, such as a flat area of intramucosal adenocarcinoma within Barrett's esophagus, carries the potential of an endoscopic cure prior to the development into a more advanced or metastatic disease. The ability to characterize a lesion to achieve an in vivo diagnosis, such as a colonic polyp, potentially affords endoscopists the ability to decide which lesions require removal and which can be safely left behind or discarded without histological assessment. Furthermore targeted biopsies, such as in the surveillance of chronic colitis, may prove to be more accurate and efficacious than the current protocol of random biopsies. An important caveat in the discussion of developing technologies in early cancer detection is the fundamental importance of a health-care system that promotes screening programs to recruit at-risk individuals. The ideal tool to optimize the use of endoscopy in population screening would be a panel of reliable biomarkers (blood, stool, or urine) that could effectively select a high-risk group, thus reducing the indiscriminate use of an expensive technology. The following review summarizes the current endoscopic imaging techniques available, and in development, for the early identification of gastrointestinal neoplasia.

Confocal microscopy in the esophagus and stomach

Probe-based confocal microscopy (pCLE) is actively being investigated for applications in the esophagus and stomach. The use of pCLE allows real-time in vivo microscopy to evaluate the microarchitecture of the mucosal epithelium. pCLE appears to be particularly useful in identifying mucosal dysplasia and early malignancies that cannot be clearly distinguished using high-definition white light endoscopy, chromoendoscopy, or magnification endoscopy. In addition, the ability to detect dysplastic tissue in real-time may shift the current screening practice from random biopsy to targeted biopsy of esophageal and gastric cancers and their precursor lesions. We will review the use of pCLE for detection and surveillance of upper gastrointestinal early luminal malignancy.

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.