Performance characteristics of optical coherence tomography in assessment of Barrett's esophagus and esophageal cancer: systematic review

Ex vivo optical coherence tomography combined with near infrared targeted fluorescence: towards in-vivo esophageal cancer detection

Early detection of (pre)malignant esophageal lesions is critical to improve esophageal cancer morbidity and mortality rates. In patients with advanced esophageal adenocarcinoma (EAC) who undergo neoadjuvant chemoradiation therapy, the efficacy of therapy could be optimized and unnecessary surgery prevented by the reliable assessment of residual tumors after therapy. Optical coherence tomography (OCT) provides structural images at a (sub)-cellular level and has the potential to visualize morphological changes in tissue. However, OCT lacks molecular imaging contrast, a feature that enables the study of biological processes at a cellular level and can enhance esophageal cancer diagnostic accuracy. We combined OCT with near-infrared fluorescence molecular imaging using fluorescently labelled antibodies (immuno-OCT). The main goal of this proof of principle study is to investigate the feasibility of immuno-OCT for esophageal cancer imaging. We aim to assess whether the sensitivity of our immuno-OCT device is sufficient to detect the tracer uptake using an imaging dose (∼100 times smaller than a dose with therapeutic effects) of a targeted fluorescent agent. The feasibility of immuno-OCT was demonstrated ex-vivo on dysplastic lesions resected from Barrett's patients and on esophageal specimens resected from patients with advanced EAC, who were respectively topically and intravenously administrated with the tracer bevacizumab-800CW. The detection sensitivity of our system (0.3 nM) is sufficient to detect increased tracer uptake with micrometer resolution using an imaging dose of labelled antibodies. Moreover, the absence of layered structures that are typical of normal esophageal tissue observed in OCT images of dysplastic/malignant esophageal lesions may further aid their detection. Based on our preliminary results, immuno-OCT could improve the detection of dysplastic esophageal lesions.

Improved FAST algorithm for non-uniform rotational distortion correction in OCT endoscopic imaging

Optical Coherence Tomography (OCT) is widely used for endoscopic imaging in endoluminal organs because of its high imaging accuracy and resolution. However, OCT endoscopic imaging suffers from Non-Uniform Rotational Distortion (NURD), which can be caused by many factors, such as irregular motor rotation and changes in friction between the probe and the sheath. Correcting this distortion is essential to obtaining high-quality Optical Coherence Tomography Angiography (OCTA) images. There are two main approaches for correcting NURD: hardware-based methods and algorithm-based methods. Hardware-based methods can be costly, challenging to implement, and may not eliminate NURD. Algorithm-based methods, such as image registration, can be effective for correcting NURD but can also be prone to the problem of NURD propagation. To address this issue, we process frames by coarse and fine registration, respectively. The new reference frame is generated by filtering out the A-scan that may have the NURD problem by coarse registration. And the fine registration uses this frame to achieve the final NURD correction. In addition, we have improved the Features from Accelerated Segment Test (FAST) algorithm and put it into coarse and fine registration process. Four evaluation functions were used for the experimental results, including signal-to-noise ratio (SNR), peak signal-to-noise ratio (PSNR), mean squared error (MSE), and structural similarity index measure (SSIM). By comparing with Scale-invariant feature transform (SIFT), Speeded up robust features (SURF), Oriented FAST and Rotated BRIEF (ORB), intensity-based (Cross-correlation), and Optical Flow algorithms, our algorithm has a higher similarity between the corrected frames. Moreover, the noise in the OCTA data is better suppressed, and the vascular information is well preserved. Our image registration-based algorithm reduces the problem of NURD propagation between B-scan frames and improves the imaging quality of OCT endoscopic images.

Comparing accuracy of high-risk features for detecting advanced neoplasia in pancreatic cystic lesions: a systematic review and meta-analysis

Background

The American Gastroenterological Association recommends endoscopic ultrasound (EUS) for evaluating pancreatic cystic lesions (PCL) with ≥2 high-risk features (HRF), whereas the American College of Gastroenterology recommends EUS for ≥1 HRF. This systematic review and meta-analysis compared the diagnostic accuracy of using ≥1 vs. ≥2 HRF for assessing the risk of advanced neoplasia (AN) and performing EUS in PCL.

Methods

An electronic database search was performed for eligible studies. AN was defined as pancreatic adenocarcinoma, intraductal papillary mucinous neoplasm or mucinous cystadenoma with high-grade dysplasia, pancreatic intraepithelial neoplasia and pancreatic neuroendocrine tumors. HRF included cyst size ≥3 cm, solid component, and dilated pancreatic duct ≥5 mm. The primary outcome was the sensitivity and specificity of using ≥1 vs. ≥2 HRF as an indication for EUS to detect AN in PCL.

Results

Of 38 studies initially screened, 8 were included in the final analysis. Seven studies assessed the accuracy of ≥2 HRF and 4 studies assessed ≥1 HRF. The pooled sensitivity, specificity, positive and negative predictive values of EUS for detecting AN were 41.7% (95% confidence interval 19.5-67.8%), 90.8% (81.9-95.5%), 30.4% (19.4-44.2%) and 94.3% (89.6-97.0%) with ≥2HRFs, and 77.1% (66.1-85.3%), 72.7% (50.4-87.5%), 17.95% (10.3-29.4%), 98.1% (90.8-99.6%), respectively, with ≥1 HRF.

Conclusion

Performing EUS for PCL with ≥1 HRF could offer greater sensitivity in detecting AN compared to ≥2 HRF, with a similar negative predictive value.

Role of optical coherence tomography in Barrett’s esophagus

Traditional endoscopic techniques for Barrett’s esophagus (BE) surveillance relied on factor of probability as endoscopists performed cumbersome random biopsies of low yield. Optical coherence tomography (OCT) is a novel technique based on tissue light interference and is set to break conventional barriers. OCT was initially introduced in ophthalmology but was soon adopted by other areas of medicine. When applied to endoscopy, OCT can render images of the superficial layers of the gastrointestinal tract and is highly sensitive in detecting dysplasia in BE. Volumetric laser endomicroscopy is a second generation OCT endoscope device which is able to identify buried glands after ablation. Addition of artificial intelligence to OCT has rendered it more productive. The newer additions to OCT such as angiogram and laser marking will increase the accuracy of investigation. In spite of the few inevitable drawbacks associated with the technology, it presently outperforms all newer endoscopic techniques for the surveillance of BE.

Modern Diagnosis of Early Esophageal Cancer: From Blood Biomarkers to Advanced Endoscopy and Artificial Intelligence

Simple Summary

Esophageal cancer (EC) has a poor prognosis when the diagnosis is delayed, but curative treatment is possible if the diagnosis is timely. The disease subtly progresses before symptoms prompt patients to seek medical attention. Effective pre-symptomatic screening strategies may improve the outcome of the disease. Recent evidence provided insights into early diagnosis of EC via blood tests, advanced endoscopic imaging, and artificial intelligence. Accordingly, we reviewed available strategies to diagnose early EC.

Abstract

Esophageal cancer (EC) is the seventh most common cancer and the sixth cause of cancer death worldwide. Histologically, esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma (EAC) account for up to 90% and 20% of all ECs, respectively. Clinical symptoms such as dysphagia, odynophagia, and bolus impaction occur late in the natural history of the disease, and the diagnosis is often delayed. The prognosis of ESCC and EAC is poor in advanced stages, being survival rates less than 20% at five years. However, when the diagnosis is achieved early, curative treatment is possible, and survival exceeds 80%. For these reasons, mass screening strategies for EC are highly desirable, and several options are currently under investigation. Blood biomarkers offer an inexpensive, non-invasive screening strategy for cancers, and novel technologies have allowed the identification of candidate markers for EC. The esophagus is easily accessible via endoscopy, and endoscopic imaging represents the gold standard for cancer surveillance. However, lesion recognition during endoscopic procedures is hampered by interobserver variability. To fill this gap, artificial intelligence (AI) has recently been explored and provided encouraging results. In this review, we provide a summary of currently available options to achieve early diagnosis of EC, focusing on blood biomarkers, advanced endoscopy, and AI.

Advanced endoscopic imaging for detecting and guiding therapy of early neoplasias of the esophagus

Esophageal cancers, largely adenocarcinoma in Western countries and squamous cell cancer in Asia, present a significant burden of disease and remain one of the most lethal of cancers. Key to improving survival is the development and adoption of new imaging modalities to identify early neoplastic lesions, which may be small, multifocal, subsurface, and difficult to detect by standard endoscopy. Such advanced imaging is particularly relevant with the emergence of ablative techniques that often require multiple endoscopic sessions and may be complicated by bleeding, pain, strictures, and recurrences. Assessing the specific location, depth of involvement, and features correlated with neoplastic progression or incomplete treatment may optimize treatments. While not comprehensive of all endoscopic imaging modalities, we review here some of the recent advances in endoscopic luminal imaging, particularly with surface contrast enhancement using virtual chromoendoscopy, highly magnified subsurface imaging with confocal endomicroscopy, optical coherence tomography, elastic scattering spectroscopy, angle-resolved low-coherence interferometry, and light scattering spectroscopy. While there is no single ideal imaging modality, various multimodal instruments are also being investigated. The future of combining computer-aided assessments, molecular markers, and improved imaging technologies to help localize and ablate early neoplastic lesions shed hope for improved disease outcome.

Artificial intelligence-assisted esophageal cancer management: Now and future

Esophageal cancer poses diagnostic, therapeutic and economic burdens in high-risk regions. Artificial intelligence (AI) has been developed for diagnosis and outcome prediction using various features, including clinicopathologic, radiologic, and genetic variables, which can achieve inspiring results. One of the most recent tasks of AI is to use state-of-the-art deep learning technique to detect both early esophageal squamous cell carcinoma and esophageal adenocarcinoma in Barrett’s esophagus. In this review, we aim to provide a comprehensive overview of the ways in which AI may help physicians diagnose advanced cancer and make clinical decisions based on predicted outcomes, and combine the endoscopic images to detect precancerous lesions or early cancer. Pertinent studies conducted in recent two years have surged in numbers, with large datasets and external validation from multi-centers, and have partly achieved intriguing results of expert’s performance of AI in real time. Improved pre-trained computer-aided diagnosis algorithms in the future studies with larger training and external validation datasets, aiming at real-time video processing, are imperative to produce a diagnostic efficacy similar to or even superior to experienced endoscopists. Meanwhile, supervised randomized controlled trials in real clinical practice are highly essential for a solid conclusion, which meets patient-centered satisfaction. Notably, ethical and legal issues regarding the black-box nature of computer algorithms should be addressed, for both clinicians and regulators.

Early Esophageal Cancer: A Gastroenterologist's Disease

Traditionally, early esophageal cancer (i.e., cancer limited to the mucosa or superficial submucosa) was managed surgically; the gastroenterologist's role was primarily to diagnose the tumor. Over the last decade, advances in endoscopic imaging, ablation, and resection techniques have resulted in a paradigm shift-diagnosis, staging, treatment, and surveillance are within the endoscopist's domain. Yet, there are few reviews that provide a focused, evidence-based approach to early esophageal cancer, and highlight areas of controversy for practicing gastroenterologists. In this manuscript, we will discuss the following: (1) utility of novel endoscopic technologies to identify high-grade dysplasia and early esophageal cancer, (2) role of endoscopic resection and imaging to stage early esophageal cancer, (3) endoscopic therapies for early esophageal cancer, and (4) indications for surgical and multidisciplinary management.

Volumetric laser endomicroscopy and optical coherence tomography in Barrett's esophagus: a systematic review and meta-analysis

Background and study aims  Endoscopic imaging of Barrett's esophagus (BE) with advanced technologies, such as optical coherence tomography (OCT) and volumetric laser endomicroscopy (VLE), allows targeted biopsies and may reduce the number of random biopsies to detect esophageal neoplasia in the early stages during endoscopic BE surveillance. The aim of this study was to evaluate the accuracy of OCT and VLE in diagnosis of intestinal metaplasia, dysplasia, and high-grade dysplasia (HGD), and intramucosal carcinoma (IMC) in BE. Patients and methods  In this systematic review and meta-analysis, the primary outcome measure was diagnostic accuracy of OCT and VLE, in comparison with the gold standard. In the meta-analysis, we calculated sensitivity, specificity, positive likelihood ratio (LR+), negative likelihood ratio (LR-), and diagnostic odds ratio (DOR) for both methods. We performed analyses by patient and by lesion. Results  We evaluated 14 studies involving a collective total of 721 patients and 1565 lesions. In the analysis by lesion, VLE showed a pooled sensitivity, specificity, LR+, LR-, DOR, and SROC AUC of 85 %, 73 %, 3.2, 0.21, 15.0, and 0.87, respectively, for detection of HGD/IMC. In the analysis by lesion for detection of HGD/EAC, OCT showed a pooled sensitivity, specificity, LR+, LR-, DOR, and summary receiver operating characteristic area under the curve of 89 %, 91 %, 9.6, 0.12, 81.0, and 0.95, respectively. The accuracy of OCT in identifying intestinal metaplasia showed a pooled sensitivity, specificity, LR+, LR-, and DOR of 92 %, 81 %, 5.06, 0.091, and 55.58, respectively. Conclusion  OCT- and VLE-guided targeted biopsies could improve detection of dysplasia and neoplasia. Further studies could determine whether the use of such biopsies might replace the current protocol.

Staging of T1 esophageal adenocarcinoma with volumetric laser endomicroscopy: a feasibility study

Background and study aims  Precise staging in T1 esophageal adenocarcinoma (EAC) is critical in determining candidacy for curative endoscopic resection. High-frequency endoscopic ultrasound (EUS) has demonstrated suboptimal accuracy in T1 EAC staging due to insufficient spatial resolution. Volumetric laser endomicroscopy (VLE) allows for high-resolution wide-field visualization of the esophageal microstructure. We aimed to investigate the role of VLE in staging T1 EAC. Patients and methods  Patients undergoing endoscopic mucosal resection (EMR) were prospectively enrolled and only T1 EAC cases were included. EMR specimens were imaged using second-generation VLE immediately after resection. VLE images were analyzed for signal intensity by depth and signal attenuation (dB/mm) in both cross-sectional and en-face orientation. A decision tree model was constructed to combine measured VLE parameters and delineate diagnostic thresholds. Results  Thirty EMR scans were obtained - 15 T1a specimens from 9 patients and 15 T1b specimens from 11 patients. T1b specimen VLE scans exhibited higher signal intensity ( P  < 0.0001) and higher signal attenuation compared to T1a specimens ( P  = 0.03). A combination of signal attenuation and signal intensity at 150 µm depth yielded optimal diagnostic thresholds and an area under the curve (AUC) of 0.77. VLE signal attenuation was significantly associated with grade of differentiation, irrespective of EAC stage. Conclusions  VLE signal intensity and signal attenuation are quantitatively distinct in T1a and T1b EAC and associated with grade of differentiation. This is the first study examining the role of VLE for staging of T1 EAC and demonstrates promising diagnostic performance. With further in vivo validation, VLE may serve a role in staging superficial EAC.

Advanced Imaging for Barrett's Esophagus and Early Neoplasia: Surface and Subsurface Imaging for Diagnosis and Management

PURPOSE OF REVIEW

Esophageal adenocarcinoma bears one of the fastest rising incidence of any cancers and generally arises in the setting of gastroesophageal reflux and Barrett's esophagus. However, early detection of neoplasia can be challenging since most patients are asymptomatic until they progress to more advanced and less curable stages, and early dysplastic lesions can be small, multifocal, and difficult to detect. Clearly, new imaging tools are needed in light of sampling error associated with random biopsies, the current standard of practice.

RECENT FINDINGS

Advances in endoscopic imaging including virtual chromoendoscopy, confocal laser endomicroscopy, and subsurface imaging with optical coherence tomography have ushered in a new era for detecting subtle neoplastic lesions. Moreover, in light of esophagus-sparing treatments for neoplastic lesions, such tools are likely to guide ablation and follow-up management. While there is no ideal single imaging modality to facilitate improved detection, staging, ablation, and follow-up of patients with dysplastic Barrett's esophagus, new advances in available technology, the potential for multimodal imaging, and the use of computer-aided diagnosis and biomarkers all hold great promise for improving detection and treatment.