Dale J. Waterhouse

Design and validation of a near-infrared fluorescence endoscope for detection of early esophageal malignancy

Abstract. Barrett’s esophagus is a known precursor lesion to esophageal adenocarcinoma. In these patients, early detection of premalignant disease, known as dysplasia, allows curative minimally invasive endoscopic therapy, but is confounded by a lack of contrast in white light endoscopy. Imaging fluorescently labeled lectins applied topically to the tissue has the potential to more accurately delineate dysplasia, but tissue autofluorescence limits both sensitivity and contrast when operating in the visible region. To overcome this challenge, we synthesized near-infrared (NIR) fluorescent wheat germ agglutinin (WGA-IR800CW) and constructed a clinically translatable bimodal NIR and white light endoscope. Images of NIR and white light with a field of view of 63 deg and an image resolution of 182  μm are coregistered and the honeycomb artifact arising from the fiber bundle is removed. A minimum detectable concentration of 110 nM was determined using a dilution series of WGA-IR800CW. We demonstrated ex vivo that this system can distinguish between gastric and squamous tissue types in mouse stomachs (p=0.0005) and accurately detect WGA-IR800CW fluorescence in human esophageal resections (compared with a gold standard imaging system, rs>0.90). Based on these findings, future work will optimize the bimodal endoscopic system for clinical trials in Barrett’s surveillance.

Emerging optical methods for endoscopic surveillance of Barrett's oesophagus

Barretts oesophagus is an acquired metaplastic condition that predisposes patients to the development of oesophageal adenocarcinoma, prompting the use of surveillance regimes to detect early malignancy for endoscopic therapy with curative intent. The currently accepted surveillance regime uses white light endoscopy together with random biopsies, but has poor sensitivity and discards information from numerous light-tissue interactions that could be exploited to probe structural, functional, and molecular changes in the tissue. Advanced optical methods are now emerging that are highly sensitive to these changes and hold potential to improve surveillance of Barretts oesophagus if they can be applied endoscopically. The next decade will see some of these exciting new methods applied to surveillance of Barretts oesophagus in new device architectures for the first time, potentially leading to a long-awaited improvement in the standard of care.

Spectral band optimization for multispectral fluorescence imaging

Multispectral imaging has the potential to improve sensitivity and specificity in biomedical imaging through simultaneous acquisition of both morphological (spatial) and chemical (spectral) information. Performing multispectral imaging in real time with spectrally resolved detector arrays (SRDAs), for example in endoscopy or intraoperative imaging, requires a direct trade off between spatial and spectral resolution. We sought to quantitatively assess the impact of spectral band selection on contrast agent detection in fluorescence endoscopic imaging. As a proof of concept, we measured the ‘ground truth’ spectra from a dilution series of a single near-infrared fluorescent contrast agent using a spectrometer incorporated into the detection path of our endoscope. We then modeled the influence of an SRDA on these spectra and calculated the theoretical endmembers associated with reflectance and fluorescence signals from the pure contrast agent. To test the accuracy of our model, we incorporated into the same endoscope an off-the-shelf SRDA with a 3x3 filter deposition pattern of 9 spectral bands. After spectral unmixing using the modeled endmembers, the amplitude of the fluorescence recorded with the SRDA compared favorably with the amplitude of fluorescence derived from the ‘ground truth’ spectra recorded with the spectrometer. In the future, this approach could be used to minimize the number of spectral bands required in a given imaging system and hence maximize the spatial resolution of the multispectral camera.

A clinically translatable hyperspectral endoscopy (HySE) system for imaging the gastrointestinal tract

These are raw and processed data of simulation and experiments in the paper (A clinically translatable hyperspectral endoscopy (HySE) system for imaging the gastrointestinal tract).

A multispectral endoscope based on spectrally resolved detector arrays

A multispectral endoscope capable of simultaneous reflectance and fluorescence imaging was developed based on spectrally resolved detector arrays. The endoscope can simultaneous image and unmix oxy/deoxygenated blood and two fluorescent dyes.

Design and validation of a near-infrared fluorescence endoscope for detection of early esophageal malignancy using a targeted imaging probe

Barrett’s esophagus is a condition that predisposes patients to esophageal cancer. Early detection of cancer in these patients can be curative, but is confounded by a lack of contrast in white light endoscopy (WLE). Application of fluorescently-labeled lectins to the esophagus during endoscopy can more accurately delineate dysplasia emerging within Barrett’s than WLE1, but strong tissue autofluorescence has limited sensitivity and dynamic range of this approach. To overcome this challenge, we synthesized a near-infrared (NIR) fluorescent lectin and have constructed a clinically translatable endoscope for simultaneous WLE and NIR imaging. An imaging fiber bundle, shielded from patient contact using a disposable catheter, relays collected light into an optical path that splits the WL reflectance and NIR emission onto two cameras for simultaneous video-rate recording. The captured images are co-registered and the honeycomb artifact arising from the fiber bundle is removed using interpolation between image points derived from individual fibers. A minimum detectable concentration of 110 nM was determined using a dilution series of IRDye800CW-lectin in black well plates. We have demonstrated the ability to use our endoscope to distinguish between different tissue types in ex vivo mouse stomachs. Future work using human ex vivo tissue specimens will determine safe illumination limits and sensitivity for dysplasia and adenocarcinoma in Barrett’s esophagus, prior to commencing clinical trials.

OC-053 Lectin-Based Near infra-red Molecular Imaging for Dysplasia Detection in Barrett’s Oesophagus: An ex-vivo Study on Human Tissue

Introduction Detection of early neoplasia in Barrett’s oesophagus (BO) by white-light endoscopy is challenging due to the inconspicuous nature of dysplasia. Molecular imaging using fluorescently labelled wheat-germ agglutinin (WGA) is a promising tool as this topically applied imaging agent shows lower binding to dysplastic versus non-dysplastic BO.1 However in an endoscopy setting, the detection of fluorescence in the blue/green range is limited by high-levels of tissue autofluorescence. This limitation can be overcome by using near infra-red (NIR) imaging. We aimed to assess in an ex-vivo model the feasibility of WGA-based NIR imaging for detection of dysplasia in BO. Methods we recruited patients with early BO-related neoplasia undergoing endoscopic mucosal resection (EMR). Freshly collected EMR specimens were sprayed with WGA-IR800CW and then imaged with a high-sensitivity NIR camera. Fluorescence images were captured and up to two punch biopsies were collected from each EMR under fluorescence guidance. The EMRs were paraffin embedded, cut every 2 mm and processed for histopathological assessment. Each section was scored by an expert GI pathologist every 1 mm to construct a pathology grid, which was manually co-registered with the fluorescence image. The mean fluorescence intensity (MFI) of cells in dysplastic and non-dysplastic areas was compared by the Wilcoxon matched-pairs signed rank test. Only EMR specimens with at least one dysplastic gland were included in the analysis. In addition, the MFI of punch biopsies taken from dysplastic and non-dysplastic areas was also compared by Mann-Whitney test. Results Ten patients were recruited at a single centre. A total of 18 EMR specimens and 33 punch biopsies were collected, of which 10 were dysplastic. In the whole EMR analysis, we found a significantly lower MFI for dysplastic versus non-dysplastic areas (P = 0.0012), in accordance with the reported reduced binding of WGA to neoplastic BO epithelium. Similarly, we found a nearly 2 fold reduction in the MFI of punch biopsies taken from dysplastic as compared to non-dysplastic (ND) areas (P = 0.0002) (Figure 1).Abstract OC-053 Figure 1 Conclusion WGA-based NIR imaging is an effective method for differentiating dysplastic from non-dysplastic BO mucosa ex vivo, which reduces the effects of tissue autofluorescence. In-vivo studies are now required to test the efficacy of this method for detecting dysplasia during endoscopic surveillance. Reference 1 Bird-Lieberman, et al. Nat Med 2012. Disclosure of Interest None Declared