What Is Optical Staining? The Principle and Application of Olympus NBI Technology

The NBI (Narrow Band Imaging) technology developed by Olympus. By using a special optical filter, it filters white light into narrow-band light waves of specific wavelengths, thereby highlighting subtle vascular changes on the mucosal surface and achieving a qualitative leap in the diagnostic accuracy of early-stage cancer.

NBI, short for Narrow Band Imaging, is an optical image enhancement technology. Its principle is to use a filter to remove the broadband spectrum from the red, green, and blue light waves emitted by the endoscopic light source, leaving only narrow-band light waves with wavelengths of 415nm, 540nm, and 600nm.

These light waves of specific wavelengths have unique biological characteristics:

Through the color and morphological contrast between these two layers of blood vessels (shallow and deep), doctors can clearly observe subtle changes on the mucosal surface, thus detecting early lesions that are difficult to identify with conventional white light endoscopy.

Ordinary white light is like daily lighting, mixing various colors to illuminate the entire tissue, but structures in deep and shallow areas are easily blurred, making it difficult to distinguish layers.

NBI mainly uses two specific colors of light: blue and green:

① Blue light has a short wavelength and shallow penetration, mainly illuminating the outermost mucosa and capillaries.

② Green light has a slightly longer wavelength and deeper penetration, capable of illuminating deeper blood vessels.

This is like using a blue light flashlight that can only clearly show dust on the desk surface, while a green light flashlight can illuminate things inside the drawer. By switching between these two types of light, NBI allows doctors to observe tissues "layer by layer," focusing on whichever layer they need.

Our blood contains hemoglobin (the substance that makes blood red), which has a characteristic: it has a strong affinity for absorbing blue and green light.

When the blue and green light from NBI irradiates blood vessels, most of the light is absorbed by the hemoglobin in the blood vessels, so the blood vessels appear very dark on the screen.

In contrast, the surrounding mucosal tissue reflects these light waves and looks relatively bright.

Blood vessels act like "light-absorbing sponges," specifically absorbing these two colors of light, making their outlines clearly "outlined" as dark lines or networks against a bright background, which are easy to identify at a glance.

NBI technology did not develop overnight. In 2001, Japanese scholar Sano Y et al. first reported the application of narrow-band imaging technology in the diagnosis of digestive system diseases.

Subsequently, Olympus Corporation co-developed this technology with the National Cancer Center East Hospital of Japan and officially applied it to endoscopic diagnosis in 2006.

After nearly 20 years of development, NBI technology has been continuously iterated and improved. From its initial basic imaging function to today's integration with magnification endoscopy, high-definition imaging and other technologies, NBI has become an important tool for early cancer diagnosis.

In September 2024, Olympus even launched a new camera based on 4K Narrow Band Imaging (4K NBI) technology, further improving image clarity and resolution.

NBI provides observation by irradiating two narrow-band wavelengths (blue light 390-445 nm and green light 530-550 nm) that are easily absorbed by hemoglobin in the blood, highlighting capillaries and mucosal micro-patterns on the mucosal surface. As cancerous tissue attempts to expand by dilating blood vessels to absorb nutrients, the mucosal surface forms complex patterns with increased capillaries as cancer progresses. Therefore, the use of NBI helps in the early detection of cancer and subsequent judgment of cancer properties.

① Detection and Localization

Doctors can observe from medium and long distances to quickly detect suspicious lesions and clearly determine the boundaries of the lesions.

② Differentiation and Diagnosis

By observing the shape of blood vessels and the morphology of glandular openings in the lesion area under NBI, doctors can analyze and judge the nature of the tumor (benign or malignant, early-stage or advanced-stage).

NBI is an alternative to chemical stains.

Traditional chemical staining (such as indigo carmine) and NBI can achieve similar visual effects, but NBI does not require spraying dyes, making the operation more convenient and non-invasive.

NBI technology is most commonly used for screening and diagnosing lesions mainly concentrated in the upper digestive tract and respiratory tract: