Narrow-band imaging optical chromocolonoscopy: advantages and limitations

Abstract

Narrow-band imaging (NBI) is an innovative optical technology that modifies the center wavelength and bandwidth of an endoscope's light into narrow-band illumination of 415 +/- 30 nm. NBI markedly improves capillary pattern contrast and is an in vivo method for visualizing microvessel morphological changes in superficial neoplastic lesions. The scientific basis for NBI is that short wavelength light falls within the hemoglobin absorption band, thereby facilitating clearer visualization of vascular structures. Several studies have reported advantages and limitations of NBI colonoscopy in the colorectum. One difficulty in evaluating results, however, has been non-standardization of NBI systems (Sequential and non-sequential). Utilization of NBI technology has been increasing worldwide, but accurate pit pattern analysis and sufficient skill in magnifying colonoscopy are basic fundamentals required for proficiency in NBI diagnosis of colorectal lesions. Modern optical technology without proper image interpretation wastes resources, confuses untrained endoscopists and delays inter-institutional validation studies. Training in the principles of "optical image-enhanced endoscopy" is needed to close the gap between technological advancements and their clinical usefulness. Currently available evidence indicates that NBI constitutes an effective and reliable alternative to chromocolonoscopy for in vivo visualization of vascular structures, but further study assessing reproducibility and effectiveness in the colorectum is ongoing at various medical centers.

Figure 1

NBI system. Different from the conventional RGB filter, the NBI filter consists of two narrow bands (415 ± 30 nm and 540 ± 30 nm, respectively) that make it possible to observe clearly superficial vascular patterns for clinical evaluation.

Figure 2

NBI colonoscopy image with non-sequential system. A: Conventional view of an Is polyp, 12 mm in diameter located in the sigmoid colon; B: NBI view clearly showing the superficial meshed vascular pattern on the polyp’s surface indicating an adenomatous polyp.

Figure 3

NBI colonoscopy image with sequential system. A: Conventional view of an IIa polyp, 20 mm in diameter located in the rectum; B: Meshed capillary vessels are clearly seen using magnifying NBI as dark brown areas diagnosing an intramucosal cancer.

Figure 4

NBI image of colorectal cancer. A: Conventional view of an IIa + IIc lesion, 12 mm in size, located in the transverse colon; B: NBI view shows a well demarcated area and meshed capillary vessels clearly visible characterized by thick diameter, branching and curtail irregularity; C: Magnifying NBI view additionally shows the presence of a nearly avascular or loose microvascular area due to histological desmoplastic changes in the stromal tissue, suggesting deep submucosal invasion; D: Histopathological analysis revealed an adenocarcinoma invading deeply into the submucosa (2500 μm) with lymphovascular invasion.