Bimodal reflectance and fluorescence multispectral endoscopy based on spectrally resolving detector arrays.

Abstract

Emerging clinical interest in combining standard white light endoscopy with targeted near-infrared fluorescent contrast agents for improved early cancer detection has created demand for multi-modal imaging endoscopes. Here, we used two spectrally resolving detector arrays (SRDAs) to realize a bimodal endoscope capable of simultaneous reflectance-based imaging in the visible spectral region and multiplexed fluorescence-based imaging in the near-infrared. The visible SRDA was composed of 16 spectral bands, with peak wavelengths in the range 463-648 nm and full width at half maximum (FWHM) between 9-26 nm. The near-infrared SRDA was composed of 25 spectral bands, with peak wavelengths in the range 659-891 nm and FWHM 7-15 nm. The spectral endoscope design was based on a ‘babyscope’ model using a commercially available imaging fiber bundle. We developed a spectral transmission model to select optical components and provide reference endmembers for linear spectral unmixing of the recorded image data. The technical characterization of the spectral endoscope is presented, including evaluation of the angular field of view, barrel distortion, spatial resolution and spectral fidelity, which showed encouraging performance. An agarose phantom tissue-mimicking containing oxygenated and deoxygenated blood with three fluorescent dyes was then imaged. After spectral unmixing, the different chemical components of the phantom could be successfully identified via majority decision with high signal to background ratio (>3). Imaging performance was further assessed in an ex vivo porcine esophagus model. Our preliminary imaging results demonstrate the capability to simultaneously resolve multiple biological components using a compact spectral endoscopy system.