{"id":14902,"date":"2021-07-07T12:56:49","date_gmt":"2021-07-07T12:56:49","guid":{"rendered":"https:\/\/clinlabint.com\/?p=14902"},"modified":"2021-07-07T12:59:11","modified_gmt":"2021-07-07T12:59:11","slug":"developments-in-optical-fibre-imaging-nano-ultrasonography-and-more","status":"publish","type":"post","link":"https:\/\/clinlabint.com\/developments-in-optical-fibre-imaging-nano-ultrasonography-and-more\/","title":{"rendered":"Developments in optical fibre imaging: nano-ultrasonography and more"},"content":{"rendered":"
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Developments in optical fibre imaging: nano-ultrasonography and more<\/h1>\/ in Featured Articles<\/a> <\/span><\/span><\/header>\n<\/div><\/section>
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Optical fibres have revolutionized clinical practice in the form of the optical endoscope, and are now providing the framework for an entirely new endoscopic paradigm: all-optical ultrasound. Here we describe a phonon probe, which offers a route towards cellular resolution acoustic imaging \u2013 while also offering new capabilities such as label-free contrast and parallel spectroscopy \u2013 for future in vivo diagnostics.<\/strong><\/h3>\n

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The optical endoscope is perhaps the most intuitive inspection tool at the disposal of a clinician. In its simplest form, it effectively recreates human eyesight. Since its original development nearly two centuries ago, it has remained one of the cornerstones of minimally invasive medical procedures. Central to its minimal invasiveness is the humble optical fibre: a flexible strand of glass the size of a human hair that conducts light. Early on it was realized that by bundling many optical fibres together, light scattered from different spatial positions of the imaging target could be transmitted through separate channels of the bundle and used to form an image at the user-end. That is, the bundle enables spatial resolution, a feat which can also be provided by a single fibre attached to scanning equipment.<\/p>\n

Resolution determines the smallest feature that can be observed by an imaging system. For example when using an optical microscope for histopathology, selecting lenses with insufficient resolution (generally correlated with magnification) may result in an inability to observe fine details within the tissue specimen. Conventional microscopy maximizes resolution with the following two parameters: short optical wavelengths and high numerical aperture lenses. However, these come with the caveats that shorter, bluer, wavelengths of light deliver more harmful energy to biological samples; and high numerical aperture lenses are often impractical to use. Unsurprisingly, endoscopy utilizes these same principles for increasing resolution, in addition to optical fibre bundles with minimized fibre-to-fibre spacing.<\/p>\n

The field of endoscopy in the 21st century has become increasingly focused on maximizing imaging resolution. One of the motivations is rather simple. Can the invasiveness of biopsies be reduced by performing in vivo histopathology? What\u2019s more, the invasiveness of a biopsy is not just limited to the excision process. Multiple excision sites, long processing times, sample viability and reusability, and the need for repeat procedures are all relevant complications in tissue diagnostics where the aim is to obtain a diagnosis as accurately and rapidly as possible. If an optical endoscope can be developed such that it contains the resolution of a bench-top microscope, the clinical community is one step closer to achieving the goal of high throughput in vivo diagnostics through optical biopsies. Endoscope developers such as Pentax and Mauna Kea have paved the way for such technology by integrating miniature optical lenses, high pixel density optical fibre bundles, miniature scanning equipment, and narrowband light sources (e.g. lasers) in place of or alongside classical endoscopic payloads. The most clinically translated of these technologies is the narrowband technique: confocal laser endomicroscopy (CLE), which, in expert hands, enables in vivo imaging comparable to ex vivo histological microscopy. In addition to providing microscopic visualizations of histology, CLE offers the unique opportunity to observe dynamic cellular processes in natural environments.<\/p>\n

Thus far CLE has proven that neoplastic tissue in the colon, esophagus, stomach, and pancreas can be differentiated from healthy tissue for conditions such as ulcerative colitis, Barrett\u2019s esophagus, and gastric cancer with accuracies in the range of 90\u201399%+ [1]. Furthermore, when coupled with conventional techniques such as chromoendoscopy for identifying suspicious tissue on the macroscopic scale, the diagnostic yield of CLE increases further which ultimately allows more accurately targeted real-biopsies while minimizing the total number of invasive procedures and related consequences such as scarring.<\/p>\n

Central to CLE and other endomicroscopy techniques, is the practice of fluorescence imaging. Since biological cells and tissue scatter light very similarly to water, it is often difficult to discern cells and sub-cellular features from their surroundings; i.e. there exists poor optical contrast. To circumvent this, the tissue is stained with molecules and proteins that absorb and re-emit light (fluorescence), and therefore allow individual cells \u2013 and even sub-cellular components such as the nucleus and cell membrane \u2013 to illuminate themselves from the perspective of the camera. Although fluorescence imaging is invaluable to the life and clinical sciences (and industry standard fluorophores such as fluorescein are known to be physiologically safe), there is great interest in developing label-free imaging techniques. Transitioning to label-free imaging would eliminate the need to closely monitor:<\/p>\n