Optical Endoscopy

- Novel Endoscopic Biophotonic Diagnostic Technologies

Novel endoscopic biophotonic diagnostic technologies have the potential to non-invasively detect the interior of a hollow organ or cavity of the human body with subcellular resolution or to obtain biochemical information about tissue in real time. With the capability to visualize or analyze the diagnostic target in vivo, these techniques gradually developed as potential candidates to challenge histopathology which remains the gold standard for diagnosis. Consequently, many innovative endoscopic diagnostic techniques have succeeded in detection, characterization, and confirmation: the three critical steps for routine endoscopic diagnosis. 

An endoscope is used in medicine to examine the interior of a hollow organ or cavity of the human body. Developments in optical imaging technology continue to promote the revolution of endoscopy. Currently, electronic chromoendoscopic techniques such as narrow-band imaging, linked color imaging and i-scan provide wide-field high-contrast video images to help endoscopists find mucosal abnormalities especially precancers. 

However, comparing with traditional histopathologic biopsy, electronic chromoendoscopy lacks the capacity to provide more detailed morphologic information about tissue and cell for accurately confirming or staging cancer. Furthermore, although existing commercial endomicroscopy including endocytoscopy or probe-based confocal laser endomicroscopy can image at cellular information, their detection range is limited to the surface of the mucosa (< 1 mm in depth) which may cause the missed diagnosis of the hidden lesions in deep tissue. 

Therefore, many studies have been conducted in numerous research centers on novel endoscopic diagnostic technologies to provide more accurate diagnostic information. The advent of these technologies in medical trial research, such as photoacoustic endoscopy (PAE), Raman spectroscopy (RS), two-photon excited fluorescence (TPEF) imaging has opened a new era and created tremendous opportunities for the enhanced identification and biochemical characterization of diseases. These modalities also have the potential to allow non-invasive in vivo “optical biopsy” which differentiates areas of similar clinical characteristics, hence challenging the ex vivo histology which is the only way for definitive cancer diagnosis. In addition, these endoscopic techniques own unprecedented temporal-spatial resolution of imaging with innovative mechanisms such as photoacoustics, optical coherent tomography, and multi-photo effect. By utilizing these novel tissue–photon interacting mechanisms, these techniques can guide biopsies by accessing the subtle mucosal/submucosal abnormalities with higher contrast, better resolution, and penetration depth. Hence, they cut down the number of biopsy times, costs, and risks for patients. 

However, most of these technologies are not mature, so they have been neither officially launched into the market nor put into clinical use in the hospital so far. Thus, well-organized large-scale animal experiments and human clinical trials should be executed to further validate and standardize these techniques before approval of the clinical application.