Abstract
Fluorescence Imaging (FI) is a powerful technique in biological science and clinical medicine. Current FI devices that are used either for in-vivo or in-vitro studies are expensive, bulky and consume substantial power, confining the technique to laboratories and hospital examination rooms. Here we present a miniaturised wireless fluorescence endoscope capsule with low power consumption that will pave the way for future FI systems and applications. With enhanced sensitivity compared to existing technology we have demonstrated that the capsule can be successfully used to image tissue autofluorescence and targeted fluorescence via fluorophore labelling of tissues. The capsule incorporates a state-of-the-art complementary metal oxide semiconductor single photon avalanche detector imaging array, miniaturised optical isolation, wireless technology and low power design. When in use the capsule consumes only 30.9 mW, and deploys very low-level 468 nm illumination. The device has the potential to replace highly power-hungry intrusive optical fibre based endoscopes and to extend the range of clinical examination below the duodenum. To demonstrate the performance of our capsule, we imaged fluorescence phantoms incorporating principal tissue fluorophores (flavins) and absorbers (haemoglobin). We also demonstrated the utility of marker identification by imaging a 20 μM fluorescein isothiocyanate (FITC) labelling solution on mammalian tissue.
Highlights
Fluorescence Imaging (FI) is a powerful technique in biological science and clinical medicine
The block is designed to accommodate the excitation and emission wavelengths of both flavin adenine dinucleotide (FAD) fluorophore (460 nm excitation, 520 nm emission) and fluorescein isothiocyanate (FITC) (480 nm excitation, 520 nm emission) that are used in this work to prove the principles of autofluorescence and targeted-fluorescence imaging respectively
Other fluorophores have emission properties suitable for detection by a silicon single photon avalanche detector (SPAD), but FAD and FITC have the same emission wavelength and a similar excitation wavelength, so we could demonstrate the function of our device with the same choice of filters
Summary
Fluorescence Imaging (FI) is a powerful technique in biological science and clinical medicine. Similar to WLE, CE uses white light imaging (WLI) and is potentially capable of viewing ailments including tumours, obscure gastrointestinal bleeding and Crohn’s disease within the small bowel[3,5,6]. Both WLE and CE suffer from low detection rate. Fluorescence endoscopy exploits the natural phenomenon whereby specific molecules (fluorophores) absorb the excitation energy of blue light (380–500 nm wavelength) and re-emit some of that energy in the form of green light (490–590 nm)[13] These fluorophores can occur naturally within human tissue (endogenous) and are utilised in autofluorescence endoscopy, or can be introduced externally as labels to the biological system (exogenous) for use in targeted-fluorescence endoscopy[7,14]. A very sensitive imager is required to keep illumination power and fluorophore concentration low and within safe limits[14,23]
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