Real-time Histology in Colonoscopy

Key points

HD endoscopy and virtual chromoendoscopy

HD white light endoscopy (WLE) became possible after introduction of technical improvements from digital broadcasting to endoscopy. In digital imaging, resolution is a function of pixel density, and is improved by incorporating high–pixel density charge-coupled device (CCD) chips. Although standard-definition endoscopes incorporated approximately 200,000 to 400,000 pixels on 576 lines, HD endoscopes provide more than 2 × 10⁶ pixels on 1080 lines, which results in visualization of subtle mucosal

AFI

The initial concept of AFI was to serve as a red-flag technology for detection of suspicious lesions. However, AFI relies on the characterization of lesions based on alterations in the contents of endogenous fluorophores such as hemoglobin, nicotinamide adenine dinucleotide (reduced form), and collagen. In AFI, sequential illumination of the mucosa with red and green light (for reflectance) and blue light (for excitation of fluorophores) results in a pseudocolored image in which neoplasia is

EC

EC is an adaption of light microscopy that provides ultrahigh magnification on contact with the mucosa of a fixed-focus, high-power lens projecting images to a CCD chip.¹⁹ Probe-based²⁰ and integrated-type²¹ EC systems (Olympus, Japan) have been evaluated that enable in vivo microscopic imaging in 450-fold to 1400-fold magnification after topical staining of the mucosa (eg, with methylene blue for delineation of nuclei, and crystal violet or toluidine blue for cytoplasmic staining). With this,

Confocal laser endomicroscopy

Confocal laser endomicroscopy (CLE) is fundamentally different from EC through the use of laser light instead of visible light. This difference enables microscopic visualization not only on the tissue surface but also below the surface after the application of a fluorescent agent. Up to 1000-fold magnification is obtained, and subcellular details can be visualized. Two systems are currently available, both using excitation with blue laser light of 488 nm: one is endoscope-integrated (eCLE;

Perspectives

Most of the methods described earlier rely on gross morphologic alterations of the tissue. Driven by progress in molecular targeted therapies for GI cancer or inflammation, molecular imaging has been a major focus of research in GI endoscopy.35, 36 Apart from wide-field detection of colonic lesions,³⁷ molecular labeling has been used for characterization of lesions based on their molecular fingerprints.38, 39 Larger studies are awaited.

All of the approaches of optical biopsies listed earlier

Summary

Diagnostic endoscopy has progressed considerably in recent years with respect to characterization of lesions and on-site microscopic imaging. Starting from magnification chromoendoscopy, HD-WLE augmented by virtual chromoendoscopy techniques significantly eased detailed endoscopic imaging. EC has provided ultrahigh light magnification. Endomicroscopy has brought confocal laser scanning microscopy into the endoscopy suite and proved its value in multiple studies. Together these tools help to