Invited PaperOptical fibers for high-resolution in vivo microendoscopic fluorescence imaging
Introduction
Over the past decades endoscopes have been used to observe inside of hollow cavity or the surface of inner organs of the human body for diagnosis or surgery in a minimally invasive or noninvasive manner [1]. An endoscope can transmit light deep into the body through optical fibers and visualize lesions that are typically inaccessible by other means. However, it has several limitations in detecting small lesions or identifying underlying microscopic pathological features. For example, the missing rate of colonoscopic diagnosis can be as high as 22% to detect adenoma [2]. Regular colonoscopy procedures cannot provide histopathologic information by itself, and sometimes require unnecessary biopsy or removal of suspected lesions for diagnosis, which often requires patients to return for additional biopsies or examinations.
Nowadays, optical fiber technology has advanced to perform real time assessment of tissue pathology. High-resolution endoscopy can help improving diagnosis of a microscopic lesions or help delineating tumor margins more accurately. This instrument is referred to as a “microendoscope” or “endomicroscope” (see Ref. [3]). Together with the development of high-resolution endoscope, fluorescence imaging has increased applications to the medical field. As fluorescence probes can be designed to bind specific target molecules, a potential indicator of pathology, fluorescence imaging allows endoscopists to identify suspicious lesions with altered fluorescence as potential biopsy. Fluorescence microendoscopy can provide distinct contrast arising from characteristics of lesions in addition to reflected white light [4].
In this review, we describe state-of-the-art fiber-based fluorescence imaging modalities using various types of optical fibers, emerging imaging techniques, and promising medical applications where microendoscopy can improve the current clinical practice.
Section snippets
The types of optical fiber for microendoscopic fluorescence imaging
The optical fiber is a key element for implementing microendoscopy for flexible maneuvering along curved lumen of animal or human organ, which is usually impractical with rigid elements. Various microendosocpic imaging modalities based on the type of optical fibers are illustrated with their specific applications.
Medical applications of microendoscopy
Early and accurate diagnosis is important for effective prevention and treatment of disease. Diagnosis of disease is often accomplished via evaluation of tissue biopsy samples. As confocal or two-photon endoscopy can achieve optical sectioning with high-resolution, these imaging modalities can be applied to the clinic. Two commercial confocal microendoscopy systems are currently in use in the clinic. The Pentax ISC-1000 (Pentax, Tokyo, Japan) confocal microendoscopy system is a miniaturized
Summary and perspective
Modern microscopic techniques using various optical fibers for high-resolution with fluorescence contrast have brought more clear view of suspicious lesion to physicians for better diagnosis and proper management. Microendoscopy based on various optical fibers has expanded the range of accessible tissues deep inside the body and resolutions down to cellular level in living experimental animals or humans in clinic. The design of endoscopic probes can be customized to accommodate a wide range of
Acknowledgments
This work is supported by grants from the Institute of Medical System Engineering at GIST, and the Bio & Medical Technology Development Program and Basic Science Research Program through the National Research Foundation (NRF) funded by the Ministry of Science, ICT & Future Planning (No. 2011-0019619, 2012R1A1A1012853, R31-2008-000-10071-0).
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