Image-enhanced endoscopy in upper gastrointestinal disease: focusing on texture and color enhancement imaging and red dichromatic imaging

Abstract

Endoscopic examination plays a crucial role in the diagnosis of upper gastrointestinal (UGI) tract diseases. Despite advancements in endoscopic imaging, the detection of subtle early cancers and premalignant lesions using white-light imaging alone remains challenging. This review discusses two novel image-enhanced endoscopy (IEE) techniques-texture and color enhancement imaging (TXI) and red dichromatic imaging (RDI)-and their potential applications in UGI diseases. TXI enhances texture, brightness, and color tone, which improves the visibility of mucosal irregularities and facilitates earlier detection of neoplastic lesions. Studies have suggested that TXI enhances the color differences between lesions and the surrounding mucosa and improves the visibility of the lesion. TXI aids in the diagnosis of various UGI diseases, including early gastric cancer, esophageal cancer, premalignant conditions such as atrophic gastritis and Barrett's esophagus, and duodenal tumors. RDI utilizes specific wavelengths to enhance the visualization of deep blood vessels or bleeding points, aiding in the rapid and accurate identification of bleeding sources during endoscopic procedures. Although promising, TXI and RDI require further large-scale studies across diverse populations to establish their clinical utility, diagnostic performance, and cost-effectiveness before integration into the guidelines. Standardized training is also required for effective utilization. Overall, these IEE techniques has the potential to improve the diagnosis and management of UGI.

Keywords: Diagnosis; Endoscopy; Gastric cancer; Image enhancement; Upper gastrointestinal tract.

Fig. 1.

Optimizing the three key elements of images in texture and color enhancement imaging (TXI). TXI emphasizes texture, brightness, and color tone to enhance the visibility of lesions. It seeks to augment the dimensional portrayal of subtle surface irregularities, enhance brightness in dark areas, and accentuate color alterations. WLI, white-light imaging.

Fig. 2.

A simplified flowchart of image processing algorithm of the texture and color enhancement imaging (TXI). Input image is initially divided into base and detail layers. Brightness correction is applied to dark regions of the base layer, and the dynamic range of the base layer is compressed to maintain local contrast. Texture in the detail layer is enhanced to improve subtle contrast. Compressed base and enhanced detail layers are then merged to generate a TXI image (mode 2). A color enhancement algorithm expands color differences, producing the final TXI mode 1 image. The goal of texture and color tone enhancement is to facilitate the recognition of structural and color tone disparities between lesions and the surrounding mucosa. WLI, white-light imaging.

Fig. 3.

Cases of upper gastrointestinal tract lesions observed using various modes of endoscopic imaging systems. (A) A case of early gastric cancer located on the posterior wall of the mid body of the stomach. The lesion is evaluated with white-light imaging (WLI), narrow-band imaging (NBI), and texture and color enhancement imaging (TXI) mode 1. (B) A case of atrophic gastritis with intestinal metaplasia evaluated with WLI, NBI, TXI mode 1, and TXI mode 2. The contrast between the lesion and the surrounding mucosa is enhanced in TXI images without darkening due to low illumination. TXI mode 2 shows an image more similar to WLI in color compared to TXI mode 1. (C) A case of esophageal low-grade dysplasia evaluated with WLI, TXI mode 1, and TXI mode 1 after Lugol solution application. TXI mode 1 highlights the redness of the lesion, clarifying its boundary, which aligns with the demarcation seen after Lugol solution application.

Fig. 4.

The red dichromatic imaging (RDI) illumination system and how it visualizes deep blood vessels. (A) The configuration of the illumination source in the EVIS X1 system (Olympus Marketing) and the wavelength properties in white-light imaging (WLI) and RDI. (B) Thick blood vessels in deep layers can be identified with improved visibility through RDI. Reproduced from Uraoka et al. Therap Adv Gastroenterol 2022;15:17562848221118302, according to the Creative Commons license.

Fig. 5.

Identification of bleeding point using red dichromatic imaging (RDI) during gastric endoscopic submucosal dissection. The bleeding point is clearly visualized in RDI mode by enhancing the contrast between the highly concentrated blood and the surrounding diluted blood pool. WLI, white-light imaging.