Endoscopic imaging: How far are we from real-time histology?

Abstract

Currently, in gastrointestinal endoscopy there is increasing interest in high resolution endoscopic technologies that can complement high-definition white light endoscopy by providing real-time subcellular imaging of the epithelial surface. These 'optical biopsy' technologies offer the potential to improve diagnostic accuracy and yield, while facilitating real-time decision-making. Although many endoscopic techniques have preliminarily shown high accuracy rates, these technologies are still evolving. This review will provide an overview of the most promising high-resolution imaging technologies, including high resolution microendoscopy, optical coherence tomography, endocytoscopy and confocal laser endoscopy. This review will also discuss the application and current limitations of these technologies for the early detection of neoplasia in Barrett's esophagus, ulcerative colitis and colorectal cancer.

Keywords: Barrett’s esophagus; Colon cancer; Confocal laser endoscopy; Endocytoscopy; High-resolution; Microendoscopy; Optical coherence tomography; Ulcerative colitis.

Figure 1

Image of fiber bundle extending through the biopsy port of a standard white-light endoscope[7].

Figure 2

Images of normal squamous tissue using the High Resolution Microendoscope. A: Endoscopic microscope image of normal squamous tissue stained with 0.05% acriflavine shows flat arrangement of squamous epithelium with round regularly spaced nuclei. The round clear spaces surrounded by the epithelium represent the papillae (arrowhead). The acriflavine in image A highlights the nuclei; B: Histopathology of same specimen. Scale bar is 100 microns.

Figure 3

High resolution microendoscope in Barrett’s esophagus: After staining with topical acriflavine, corresponding microendoscopic and histopathological images are shown of Barrett’s metaplasia/LGD (A, B) and high grade dysplasia (C, D). The uniformly shaped and spaced glands with intact nuclear polarity can easily be differentiated from the crowded, back-to-back glandular architecture noted in HGD.

Figure 4

Endocytoscopy enables visualization of different cytological and architectural features, including size, arrangement and density of cells (adapted with permissionp[51]).

Figure 5

Confocal laser endoscopy image of Barrett’s metaplasia (A) and high grade dysplasia (HGD) (B) after the intravenous administration of 5 mL of intravenous fluorescein as an exogenous contrast agent. The fluorescein enhances the subepithelial capillary network. HGD can be distinguished from non-neoplastic Barrett's esophagus by the branching, irregular capillary network and irregular, thickened basement membrane.

Figure 6

Normal colonic mucosa seen with a confocal endomicroscope. Glands are seen longitudinally but are well organized and homogenous. Goblet cells appear black.