Hyperspectral imaging techniques measure spatial and spectral information, which enables discrimination between healthy tissue and lesions. Hyperspectral imaging applications in endoscopy for clinical diagnostic applications are still limited due to image distortion challenges that arise when working with a flexible endoscope, for example in the gastrointestinal tract. Here, we developed a hyperspectral endoscopy (HySE) system by exploiting a line-scanning spectrograph to measure spectral information at high spectral resolution and combining it with a CMOS camera that records wide-field images for hyperspectral image reconstruction. Moreover, we developed an image normalisation method using near-infrared light to obtain accurate hyperspectral signals by correcting uneven illumination conditions during clinical endoscopy. Our next step is to apply HySE to patients to identify abnormal features in the gastrointestinal tract in vivo.
Barrett’s oesophagus is an acquired condition that predisposes patients to the development of oesophageal adenocarcinoma through intermediate stages of dysplasia. Early detection of dysplasia allows curative endoscopic therapy, but current standard of care surveillance achieves only around 40% sensitivity for dysplasia.
Multispectral imaging (MSI) allows simultaneous collection of morphological (spatial) and biochemical (spectral) information from tissue, which can help to more effectively delineate disease. This motivated the design and construction of a compact, clinically translatable multispectral endoscope (MuSE) that can be introduced through the accessory channel of a standard gastroscope to collect multispectral images in vivo.
MuSE is based around a spectrally resolved detector array (SRDA) with 9 spectral filters (8 narrow bands; average FWHM 30nm, center wavelengths 553, 587, 629, 665, 714, 749, 791, 829nm; 1 broadband; 500–850nm). The SRDA was coupled to a clinically approved 10,000-fibre endoscope (PolyScope) for imaging. Illumination was provided by sequentially by a broadband (400–750nm) and narrowband (400–480nm) source for reflectance and autofluorescence imaging respectively.
Subjects due to undergo clinically indicated endoscopy with a previous diagnosis of dysplasia or early adenocarcinoma were enrolled for experimental imaging using MuSE in a pilot clinical study. Patients with clearly visible lesions were selected to allow co-registration of the image cubes with pathology of biopsies. Here, we present the results from these first-in-human tests of MuSE, including evaluation of the image quality and classification potential of the multispectral image cubes.
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 fluorescence-based 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.
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