Narrow Band Imaging for the Detection of Neoplastic Lesions of the Colon

Abstract

Narrow band imaging (NBI), a technology initially produced by Olympus Medical Systems of Tokyo, Japan, is a relatively new and well-recognized advancement in endoscopic imaging. Other manufacturers have variations of NBI that are similar but not as widely used. The present article will use NBI as a reference point; however, it is recognized that other manufacturers have similar systems with different names that will not be addressed further in the present discussion. The main goal of NBI technology is the ability to predict pathology in real time, based on the mucosal and vascular enhancement offered by endoscopes that have this capability. The purpose of the present paper is to discuss the clinical situations in which NBI technology is used for the detection of neoplastic lesions of the colon as well as the current evidence for or against these practices. Dr Mitchell Lee Although conventional white-light (CWL) imaging uses the entire spectrum of visible light (400 nm to 700 nm), NBI technology is based on the use of optic filters to isolate two specific bands of light: 415 nm (blue) and 540 nm (green) (1–3). By using the different absorptive and reflective properties of these wavelengthts of light on mucosa, an image that enhances the visualization of superficial vascular structures (blue: superficial capillary; green: subepithelial vessels) (1–3) is created. The NBI mode on an endoscope, which can be activated or deactivated by an endoscopist with a control button on the endoscope, typically darkens the appearance of the vessels. Examples of NBI images taken at the St Paul’s Hospital, Vancouver, British Columbia, are shown in Figure 1. Figure 1) Representative photographs of narrow band imaging (NBI) with the endoscope NBI mode deactivated (left panel) and NBI activated (right panel) NBI is often referred to as ‘digital chromoendoscopy’ (4), because it was developed as an alternative method of enhancing the mucosa and vasculature similar to that seen in chromoendoscopy, a technique in which the mucosa is sprayed with a dye (ie, indigo carmine) during the endoscopy procedure. In chromoendoscopy, the absorptive property of the dye, rather than the properties of the light shining onto the surface of the mucosa, is used to enhance the image. The images produced by chromoendoscopy are very similar to the images produced by NBI, with minor differences (5). Although chromoendoscopy is frequently used in Japan, it has not received the same popularity in North America because it is believed by many to be more time consuming to apply the dye, and may require specialized training to perform properly. In the upper gastrointestinal tract, NBI has been used for various disorders such as gastroesophageal reflux disease, Barrett’s esophagitis and gastric neoplasia (3,6–9). In the lower gastrointestinal tract, NBI has been used to detect and assess colon polyps (particularly those that are flat), and for surveillance colonoscopy in patients with ulcerative colitis (UC) and hereditary nonpolyposis colon cancer (HNPCC) (10–13). NBI has also been used in a variety of applications outside of gastroenterology such as laryngoscopy (14) and cystoscopy (15).