Application of Narrow-Band Imaging in Esophageal Cancer

Introduction:

The esophagus is an important part of the digestive tract. This is also known as the food pipe through which ingested food is passed from the mouth to the lower portion of the gastrointestinal tract. As a part of the upper gastrointestinal tract, the esophagus withstands a significant amount of noxious stimuli like smoke and irritant substances like alcohol. These substances are responsible for cancerous changes in the esophagus. Esophageal cancer is the eighth most common cancer in the world. As a result, early diagnosis of cancer may save lives and can improve the quality of life.

What Is Narrow-Band Imaging?

Endoscopy is a procedure in which a camera-like device is inserted into the body with the help of a flexible tube-like structure. This helps visualize the organs from the inside. Traditional endoscopy is also known as white-light endoscopy. However, smaller details and tissue changes can be missed in this procedure. Narrow-band imaging is nothing but an endoscopic procedure that provides high-resolution and magnified imaging of the gastrointestinal tract.

One of the main advantages of narrow-band imaging is that it can detect tissue changes without applying dyes. As a result, the chances of tissue irritation and cytotoxicity are reduced. Also, mucosal and vascular patterns can be visualized. Magnified views can be useful in detecting in-depth analysis of the subsurface changes.

How Does Narrow-Band Imaging Work?

• Unlike traditional endoscopes, narrow-band imaging techniques utilize red-green-and-blue filters. These filters help diagnose minute tissue changes based on changes in the light-reflecting patterns.

• Malignant and pre-malignant conditions are known for changes in their vascular patterns and mucosal thicknesses. Such changes can be difficult to identify through normal imaging and the naked eye. As a result, changes in their light-reflecting pattern can be useful.

• Blue light filters act on 400-430 nanometers of light. This filter can detect changes in the capillaries and superficial mucosal patterns. Absorption of hemoglobin by the tissue can also be detected.

• Greenlight filters act on the wavelength of 525 to 555 nanometers and detect changes in deep mucosa. Another advantage of this type of imaging is the capability of near focus.

• This endoscopy can take pictures from a distance of two to six millimeters with an optical magnification of 150 times.

What Does Narrow-Band Imaging Detect?

Narrow-band imaging is a potent tool for the visualization of the gastrointestinal tract. In the esophagus, narrow-band imaging (NBI) can help detect various abnormalities, such as

• Early-stage esophageal cancer.

• Barrett’s esophagus (a precancerous condition).

• Esophagitis (inflammation of the esophagus).

• Vascular lesions.

Apart from this, it enhances the visualization of mucosal patterns and blood vessels, aiding in the identification of these conditions during endoscopic examinations. NBI is particularly valuable for detecting subtle changes that may not be easily visible with conventional imaging techniques.

What Are the Applications of Narrow-Band Imaging in Barrett’s Esophagus?

Barrett’s Esophagus is a precancerous condition in which changes can be seen in the esophageal lining. Chronic inflammation is the main factor for this condition. Gastroesophageal reflux disorder is the primary pathological condition associated with this. Continuous backflow of the acidic contents from the stomach destroyed the esophageal lining. In response to the acidic contents, squamous epithelial cells secret inflammatory mediators like interleukins. As a result, the aggregate of the T-lymphocytes can be observed beneath the epithelium. Irregular and distorted mucosal patterns can be seen in narrow-band imaging of the esophageal surface epithelium. Along with this, abnormal branching with tortuous vascular patterns can be identified. Five distinct patterns can identify dysplastic changes in the mucosa.

These are:

• Type A- In this pattern, round pits and irregular microvascularisation can be seen.

• Type B- In this type, ridges and villous patterns can be seen along with a pitted appearance. Regular microvasculature can also be observed.

• Type C- In this pattern, pits and irregular microvascularization are absent. On the histological examination, interstitial metaplasia (abnormal cellular appearance due to carcinoma)can be observed.

• Type D- This pattern denotes a high grade of metaplasia with distorted pits and irregular microvasculature.

• Type E- This exhibits a more tortuous pattern along with twisted and irregular microvasculature.

How Does Narrow-Band Imaging Detect Carcinoma?

Squamous Cell Carcinoma of the Esophagus is the cancer of the food pipe known as esophageal cancer. This is the sixth most common cancer in the world. Smoking, excessive alcohol consumption, and gastroesophageal reflux disorder are the potential risk factors for developing esophageal carcinoma. The risk of squamous cell carcinoma in Asian males is four times higher. That is why the diagnosis of squamous cell carcinoma of the esophagus is important. The interepithelial capillary loop pattern is the main diagnostic feature of squamous cell carcinoma.

Other than these changes in the capillary-like dilation of the vessels, tortuosity and variations in the shapes and sizes can be seen. Apart from this, features like thick bluish to large greenish vessels and tree branch-like vessels formation in the horizontal direction of interepithelial capillary loops can be seen due to the tumor invasion. Tumor invasion is also correlated to the abnormal thickening of the mucosa and avascular area formation. The brownish-dotted appearance of the mucosa signifies a high degree of tumor invasion. This brownish area is formed due to epithelial keratinization. The grading of esophageal cancer based on narrow-band imaging is as follows:

• Type A: This is a non-invasive condition in which abnormal interepithelial capillary loop patterns can be seen.

• Type B1: This is related to high-graded, high-graded interepithelial neoplasia with involvement up to lamina propria can be seen. The irregular arrangement of the interepithelial capillary loop with severe dilation can be seen.

• Type B2: In this type, squamous cell carcinoma growth up to the muscularis mucosa can be seen. The depth of invasion is less than 200 micrometers. The interepithelial capillary loop shows severe dilation and loss of loop patterns.

• Type B3: In this condition, the invasion of the cancerous growth is more than 200 micrometers. Severe dilation of the vessels can be seen.

• Esophageal Adenocarcinoma: In this condition, carcinomatous growth can be seen in the glandular cells of the esophageal epithelium. A salmon-pink appearance of the esophageal mucosa above the level of the gastroesophageal junction can be observed.

Conclusion:

Early detection of cancerous changes can help save lives. Also, the extent of the surgical interventions can be reduced. The endoscopy procedure is a non-invasive method of detecting carcinomatous changes. But, normal white-light imaging in endoscopy is not that potent in detecting early changes. Narrow-band imaging, being an advanced endoscopic technology, uses light filters to detect tissue and capillary changes. Also, a magnified view in very close-up conditions can be potent enough to detect in-depth tissue changes. Without a doubt, it can be used to diagnose lesions in the digestive tract.