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 (NIR) fluorescent contrast agents for improved early cancer detection has created demand for multimodal imaging endoscopes. 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 fluorescencebased imaging in the NIR. The visible SRDA was composed of 16 spectral bands, with peak wavelengths in the range of 463 to 648 nm and full-width at half-maximum (FWHM) between 9 and 26 nm. The NIR SRDA was composed of 25 spectral bands, with peak wavelengths in the range 659 to 891 nm and FWHM 7 to 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 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.

A background correction method to compensate illumination variation in hyperspectral imaging

“…Finally, we focused on the influence of background correction on reflectance and absorbance hypercubes. Further work would be needed to understand how well the method could perform for other HSI applications, such as multiplexing of fluorescence contrast agents [12].…”

“…Analysis of the resulting 3D data set, or 'hypercube', enables spatial discrimination of healthy and abnormal tissues based on the rich morphological and biochemical information contained within the spatial and spectral features [2,3]. HSI has shown potential in a range of biomedical applications, from label-free tumour diagnoses [4][5][6] and detection of tumour margins during surgical operations [7][8][9], to quantification of blood oxygenation levels [10][11][12], and multi-colour fluorescent imaging [12,13]. HSI methods have thus been developed for the fast and accurate analysis of biological samples ex vivo [14][15][16][17] as well as for diagnostic and intraoperative applications in vivo [16,18].…”

Laparoscopic system for simultaneous high-resolution video and rapid hyperspectral imaging in the visible and near-infrared spectral range

“…Two systems are capable of investigating both the visible and near-infrared range, but are limited by long acquisition times and without color video during spectral imaging or low spectral resolution. 13,14 Simultaneous hyperspectral data and color video acquisition in the visible range were achieved with pushbroom and manual line-scanning flexible endoscopes. 15,16 Most systems are using spectral scanning methods like acousto-optical tunable filter (AOTF), liquid crystal tunable filter (LCTF), filter wheels, or light sources with monochromators.…”

“…Spectrally resolving detector arrays (SRDA) or snap-shot imagers are nonscanning systems and are, therefore, not limited by motion artifacts. 13 However, spatial and spectral resolutions are reduced. Spatial or pushbroom scanning allows high spectral and spatial resolution at the same time.…”

The Automatic Undistortion Strength Estimation for Any Describable Optical Distortion

“…Problems with optical distortions occur not only in normal cameras. One of the most recent research in [12] faces to the distortion also in microscopy systems, where the determination of the precise pixel position is important. The achieved correction and advanced image processing ensures the capability to simultaneously resolve multiple biological components using a compact spectral endoscopy system.…”