Elsevier

Lung Cancer

Volume 69, Issue 2, August 2010, Pages 194-202
Lung Cancer

Narrow band imaging with high-resolution bronchovideoscopy: A new approach for visualizing angiogenesis in squamous cell carcinoma of the lung

https://doi.org/10.1016/j.lungcan.2010.04.023Get rights and content

Abstract

Objectives

We investigated the ability of a high-resolution bronchovideoscopy system with narrow band imaging (NBI) to detect blood vessel structures in squamous cell carcinoma (SCC) of bronchi, as well as squamous dysplasia.

Methods

Seventy-nine patients with either abnormal sputum cytology or lung cancer were entered into the study. First, high-resolution bronchovideoscopy with white light was performed. Observations were repeated using NBI light to examine microvascular structures in the bronchial mucosa. Spectral features of the RGB (red/green/blue) sequential videoscope system were changed from a conventional RGB filter to the new NBI filter. The wavelength ranges of the NBI filter were: 400–430 nm (blue), 400–430 nm (green) and 520–560 nm (red).

Results

The following were clearly observed with NBI with high-resolution bronchovideoscopy: increased vessel growth and complex networks of tortuous vessels of various sizes, in squamous dysplasia; some dotted vessels, in addition to increased vessel growth and complex networks of tortuous vessels, in ASD; several dotted vessels and spiral or screw type tumor vessels of various sizes and grades, in SCC. Capillary blood vessel and/or tumor vessel mean diameters of ASD, CIS, microinvasive and invasive carcinoma were 41.4 ± 9.8 μm, 63.7 ± 8.2 μm, 136.5 ± 29.9 μm and 259.4 ± 29.6 μm, respectively. These results indicated a statistically significant increase of mean vessel diameters in the four groups (P < 0.0001).

Conclusion

NBI with high-resolution bronchovideoscopy was useful for detecting the increased vessel growth and complex networks of tortuous vessels, dotted vessels and spiral or screw type tumor vessels of bronchial mucosa. This may enable detecting the onset of angiogenesis during multi-step carcinogenesis of the lung.

Introduction

Narrow band imaging (NBI) is a new optical technology of modified white light using special blue and green light that can clearly visualize microvascular structures in the mucosal layer [1], [2]. NBI is now classified as an image enhanced endoscopy (IEE) technology and is available to the entire field of endoscopy combined with conventional white light instruments [3], [4]. The advantage of NBI over other techniques is its ability to enhance fine superficial microvessel patterns [5], [6]. Since the development of NBI, some investigators have reported that this new technology can provide clear images of vascular structures in some organs especially the GI tract [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17]. NBI may also allow for better detection of early preneoplastic and neoplastic mucosal lesions and may improve the effectiveness of endoscopic surveillance and screening. Moreover, in the field of bronchovideoscopy, we have also reported that high magnification bronchovideoscopy combined with NBI was useful for detecting capillary blood vessels in angiogenic squamous dysplasia (ASD) lesions [13]. Using high magnification bronchovideoscopy combined with NBI, increased vessel growth and complex networks of tortuous vessels, in addition to several dotted vessels, were identified in dysplastic mucosa or angiogenic dysplastic mucosa.

Angiogenesis that is essential for tumor growth was first recognized by Folkman [18], [19]. In order to progress to a larger size, incipient neoplasia must develop angiogenic capabilities. Several studies investigating the multi-step model of carcinogenesis in epithelial tumors have shown that angiogenesis is required, in addition to molecular changes [20]. An angiogenic switch appears to occur in pre-invasive lesions prior to invasive tumor formation in transgenic mouse models and human cancer pathogenesis studies [21], [22]. However, except for a few studies, these studies were done on tissue sections retrospectively obtained from surgical or biopsied specimens. In vivo investigations to evaluate tumor angiogenesis during multi-step carcinogenesis is desirable for diagnostic efficacy.

In a previous study, we showed angiogenesis only in bronchial dysplastic lesions using high magnification bronchovideoscopy combined with NBI at sites of abnormal fluorescence established by fluorescence bronchoscopy [13]. In the present study, we investigated the ability of a high-resolution bronchovideoscopy system with NBI to detect and visualize blood vessel structures in squamous cell carcinoma of the bronchi, including carcinoma in situ (CIS), microinvasive carcinoma and invasive carcinoma, as well as dysplastic bronchial epithelium, including ASD lesions, without using fluorescence bronchoscopy.

Section snippets

Narrow band imaging

The conventional RGB sequential videoscope system has a xenon lamp and rotation disk with 3 RGB optical filters. The rotation disk and monochrome CCD are synchronised and three band images are generated sequentially. Colour images can be synthesised using three band images with the video processor. Narrow band imaging, developed in conjunction with the Olympus Optical Corp., Tokyo, Japan, is a novel system that can be used to observe microvessel structure using a new narrow band filter on an

Pathological diagnosis of biopsy specimens

Biopsy specimens from abnormal sites were diagnosed as 37 bronchial squamous dysplasias including 22 ASD, 5 CIS, 5 microinvasive carcinomas and 14 invasive squamous cell carcinomas. Two laryngeal carcinomas in situ and one laryngeal invasive carcinoma were also diagnosed in the same session.

High-resolution bronchovideoscopic white light image and the corresponding NBI image

Fig. 2A shows high-resolution bronchoscopic findings with white light and NBI at the bifurcation of Rt B6 and the basal bronchus of a patient with sputum cytology suspicious for malignancy. Increased vessel

Discussion

NBI is now classified as an IEE technology, that can be divided into two categories, dye-based IEE and equipment-based IEE [4]. Optical and electronic technology have both been enabled in equipment-based IEE, which was applied to NBI, or spectral estimation technology and surface enhancement. NBI technologies have been well evaluated and established in the field of gastrointestinal endoscopy and applied to detailed inspections for pathological diagnosis. Recently, there are some reports

Conflict of interest

All authors have none declared.

Funding

Supported, in part, by Grant-in-Aid for Scientific Research (C) 18591541 from Japan Society for the Promotion of Science to Kiyoshi Shibuya.

Acknowledgements

We wish to thank K. Gono, T. Takigawa and S. Takehana (Olympus Optical Corp., Tokyo, Japan) for their technical assistance.

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