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Confocal imaging at high resolution is possible using an
exogenous fluorescence technique. Potentially suitable agents are
fluorescein, acriflavine, tetracycline, or cresyl violet. The most commonly
used contrast agents are acriflavine hydrochloride (0.05% in saline; topical
use only) or fluorescein sodium (5-10 ml of a 10% solution; intravenous
application). Confocal imaging following staining with acriflavine
hydrochloride and fluorescein sodium shows the characteristic morphology of
mucosal tissue. Whereas topically used acriflavine hydrochloride
strongly labels the superficial epithelial cells, including nuclei,
intravenously administered fluorescein sodium distributes throughout the
entire mucosa, with strong contrast in the connective tissue and the
capillary network. Fluorescein binds to serum albumin, and remaining unbound
dye molecules pass across the systemic capillaries and enter the tissue,
highlighting the extracellular matrix. Confocal images can be generated
simultaneously with endoscopic images, making it possible to identify
typical histological structures in the upper and lower gastrointestinal
tract. |
