Feasibility of the Ultrasmall Composite Optical Fiberscope System for Lung Cancer Observation

Peripheral pulmonary lesions (PPLs), which include pulmonary nodules and masses, are a common problem in pulmonology practice. The incidence of PPLs will likely increase given the growing adoption of chest CT screening for lung cancer. There are several guidelines available for management of PPLs. If bronchoscopy is selected as the method of diagnosis, conventional bronchoscopy has been one platform used for decades to diagnose PPLs. However, conventional bronchoscopic techniques have significant limitations and overall low diagnostic yield for most PPLs. As a result, innovative bronchoscopic techniques and technologies have evolved over the last decade to diagnose PPLs more accurately. However, accessing to PPLs located in the most peripheral part is still challenging.

As a new method to diagnose and localize cancers, photodynamic diagnosis (PDD) has been gaining attention. PDD is a new technique where a photosensitizer injected intravenously accumulates in the abnormal lesion, then its fluorescence can be detected by a detector. To conduct PDD for PPLs, we collaboratively developed a parallel-type composite optical fiberscope (COF) with an outer tip diameter of 0.97 mm with OK Fiber Technology (Kyoto, Japan). Its small size and flexibility of the tip enable it to be inserted into animal ultrasmall airways. The outer membrane of the fiberscope is made from polytetrafluoroethylene in the COF's insertable section and is hydrophilic coated, which reduces frictional forces when in the contact with the bronchial wall resulting in smooth insertion of the fiberscope. As the COF has illumination fibers and a laser fiber inside, simultaneous white-light and fluorescence imaging with real-time monitoring can be performed to confirm the tip position of the fiberscope during laser irradiation. In this study, we want to evaluate the COF regarding the quality of white-light images and the accessibility of lung tumors located in the peripheral area of the lung.