What are we looking at? Making sense of all of the new imaging technology

It is both an exciting and challenging time for diagnostic endoscopy. The latest endoscopy platforms provide sharp, high-resolution images of the gastrointestinal tract that help us distinguish subtle mucosal and vascular patterns. By itself, this represents a significant improvement in performance compared to standard-definition endoscopy. In parallel, several advanced imaging modalities have emerged that provide us with the ability to look at the gastrointestinal tract from a whole new perspective. The application of advanced imaging technologies promises to enhance our diagnostic capability and aid in real-time decision-making. Despite the hype surrounding several of these technologies, there are several things to consider when implementing advanced imaging into our practice.

What do we hope to achieve by implementing advanced imaging into our practice?

Applications for advanced imaging are broad — ranging from detection of early neoplasia to predicting relapse in inflammatory bowel disease — and depend largely on the needs of an individual practice. Perhaps one of the most studied indications is the use of advanced imaging in Barrett’s esophagus (BE) surveillance. BE-associated dysplasia can be of focal nature, heterogeneously distributed and endoscopically indistinguishable from surrounding non-dysplastic BE, providing an opportunity to enhance detection with the use of advanced imaging. The Preservation Incorporation of Valuable Endoscopic Innovations (PIVI) from the ASGE outlines the minimal diagnostic thresholds that an imaging modality should achieve in order to replace the standard random biopsy surveillance protocol.1 To date, digital chromoendoscopy and confocal laser endomicroscopy are the only two imaging modalities to meet these thresholds, but the narrow imaging field of confocal laser endomicroscopy has limited its clinical application in BE surveillance. Novel technologies such as volumetric laser endomicroscopy (VLE) are currently under study. VLE was designed specifically for BE surveillance and incorporates wide-field cross-sectional imaging with microscopic resolution. These are features that (in theory) should increase our diagnostic yield for BE dysplasia. VLE is estimated to have a sensitivity of 86 percent and specificity of 88 percent for detection of BE dysplasia based on ex-vivo imaging studies.2 A retrospective study that compared a standard BE surveillance protocol to VLE laser-targeted biopsies suggests an incremental yield for BE dysplasia with in-vivo VLE but prospective data is needed to adequately quantify this effect.3

How confident are we in our interpretation of an advanced imaging modality?

The use and interpretation of advanced imaging modalities is not routinely incorporated into gastroenterology training. Even commonly available tools such as narrow-band imaging require training in image interpretation. In other words, if an advanced imaging modality meets the thresholds set by the ASGE PIVI, its use is still limited to endoscopists with training in image interpretation. Studies have looked at the learning curve to achieve image interpretation proficiency for various imaging modalities. For example, a recent study showed that most novice VLE users require review of at least 96 single frame images to distinguish between gastric, squamous and BE with and without dysplasia.4 However, identification of a region of interest within a full VLE scan (1,200 frames) is a more complex endeavor given feature variability across multiple frames. There appears to be a high degree of consensus in identifying a region of interest amongst VLE experts asked to review a full scan, but the generalizability of this finding needs further validation.5 Time constraints associated with real-time image interpretation may also impact the diagnostic performance of an imaging modality in a clinical setting. Thus, computer-aided image enhancement and diagnosis are instrumental tools in the implementation of advanced imaging modalities into practice.

What else should we consider before implementing advanced imaging into our practice?

Training of allied health care staff on the set-up and use of advanced imaging equipment is integral to incorporating this technology into our practice. In the case of VLE, imaging probes come in various sizes that should be readily available for selection based on patient anatomy. Cost and reimbursement are also important factors to consider. There are limited data on cost analysis for novel technologies compared to standard of care, but studies do suggest a reduction in number of required biopsies with the use of advanced imaging modalities. Finally, as technology evolves, it is important to consider the clinical and potentially legal implications of its use. If an ‘optical biopsy’ is to serve as a surrogate to a histologic diagnosis, it is important to document the specific features associated with the diagnosis and to store imaging data for future reference.

In summary, the application of advanced imaging has great potential to enhance our diagnostic practice but its use should be weighed carefully against our confidence in image interpretation. The integration of computer-aided image enhancement and diagnosis is an instrumental step in the translation of advanced imaging into clinical practice.

Disclose: Dr. Leggett has received indirect research support from NinePoint Medical but no direct monetary compensation.

References

1. Committee A.T., Thosani N., Abu Dayyeh B.K., et al. ASGE Technology Committee systematic review and meta-analysis assessing the ASGE Preservation and Incorporation of Valuable Endoscopic Innovations thresholds for adopting real-time imaging-assisted endoscopic targeted biopsy during endoscopic surveillance of Barrett’s esophagus. Gastrointest Endosc. 2016;83:684-98 e7.

2. Leggett C.L., Gorospe E.C., Chan D.K., et al. Comparative diagnostic performance of volumetric laser endomicroscopy and confocal laser endomicroscopy in the detection of dysplasia associated with Barrett’s esophagus. Gastrointest Endosc. 2016;83:880-888e2.

3. Alshelleh M., Inamdar S., McKinley M., et al. Incremental yield of dysplasia detection in Barrett’s esophagus using volumetric laser endomicroscopy with and without laser marking compared with a standardized random biopsy protocol. Gastrointest Endosc. 2018;88:35-42.

4. Trindade A.J., Inamdar S., Smith M.S., et al. Learning curve and competence for volumetric laser endomicroscopy in Barrett’s esophagus using cumulative sum analysis. Endoscopy. 2018;50:471-478.

5. Kamboj A.K., Kahn A., Wolfsen H.C., et al. Volumetric laser endomicroscopy interpretation and feature analysis in dysplastic Barrett’s esophagus. J Gastroenterol Hepatol. 2018;33:1761-1765.

Join the discussion

Your email address will not be published. Required fields are marked *