Fluorescence In Vivo Endomicroscopy
Figure 3: Sequential images captured in real time during ongoing endoscopy of a single villus in the patient’s terminal ileum after i.v. administration of the fluoro- phore fluorescein sodium. The process of shedding a single epithelial cell is observed over a period of 1–2 min. (A) The epithelial cells of an intestinal villus begin form singular “gaps,” and there is an accumulation of fluorescein around neighboring cells. (B) An epithelial cell is ejected leaving a small plume of fluorescein, and the adjacent cells are beginning “zip up” the gap, restoring barrier function first from the basement membrane toward the luminal side. (C) The adjacent cells have almost formed a uniform arrangement. Further closing the gap. (D) Barrier function appears to be restored as the necessary cell-to-cell junctions consolidate. Images courtesy of Prof. Dr. Ralf Kiesslich, medical director Helios Dr. Horst Schmidt Clinics, Wiesbaden; and Prof. Dr. med. Martin Götz, Chief Physician Gastroenterology / Oncology, Sindelfingen-Böblingen Clinic, Boeblingen. Scale bars=100 µm.
subepithelial layers, and mucosal capillary network. Ex vivo staining with acriflavine-stained epithelial cell nuclei and the histoarchitecture correlated well with the histology of biopsy specimens. Musani studied normal human airway histology and endobronchial adenocarcinoma and compared FIVE with a traditional surgical histopathology approach. Images cap- tured from the trachea, primary and secondary carinae, and endobronchial mass showed cellular and subcellular structures of the respiratory mucosa and submucosa, and allowed imag- ing of pseudostratified columnar epithelium, lamina propria, and microvasculature that distinguished normal airway epi- thelium and malignant tissue [45]. Acute lung injury (ALI) and acute respiratory distress
syndrome (ARDS) are life-threatening conditions character- ized by severe acute hypoxemic respiratory failure and bilat- eral lung infiltrates [46]. ALI/ARDS must be differentiated from other acute pulmonary disease entities, but there are no “easy-to-do” diagnostic tests. Te gold standard is open lung biopsy, which has a relatively low benefit/harm ratio [47]. In
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theory, FIVE can provide cellular and structural assessment of living tissue using a small confocal probe in direct contact with the visceral pleura, and this theory was tested in a rat model of lung injury [48]. FIVE facilitated visualization of the micro- capillary network around alveoli, epithelial cell membranes, lung cell apoptosis, neutrophil extravasation, and pulmonary edema. Tese results were confirmed with ex vivo fluorescent methods (Figure 4) and suggested FIVE as a promising tool for improving bedside diagnostic and decision-making thera- peutic strategy in patients with ALI. Studies of CLE, including FIVE, for lung imaging was reviewed by Lesur [49]. Brain imaging. Fluorescence-based imaging techniques
are emerging as valuable tools in neurosurgery to high- light vascular structures and tumors (Figure 5). In a study of patients with brain neoplasm, FIVE was used intraoperatively aſter injecting i.v. fluorescein. A total of 20,734 CLE images were correlated with 267 biopsy specimens, and FIVE specific- ity and sensitivity were 94% and 91% for gliomas and 93% and 97% for meningiomas [3]. In a similar study, FIVE imaging in
www.microscopy-today.com • 2021 May
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