In vivo subsurface morphological and functional cellular and subcellular imaging of the gastrointestinal tract with confocal mini-microscopy.

AIM: To evaluate a newly developed hand-held confocal probe for in vivo microscopic imaging of the complete gastrointestinal tract in rodents.
METHODS: A novel rigid confocal probe (diameter 7 mm) was designed with optical features similar to the flexible endomicroscopy system for use in humans using a 488 nm single line laser for fluorophore excitation. Light emission was detected at 505 to 750 nm. The field of view was 475 microm multiply 475 microm. Optical slice thickness was 7 microm with a lateral resolution of 0.7 microm. Subsurface serial images at different depths (surface to 250 microm) were generated in real time at 1024 multiply 1024 pixels (0.8 frames/s) by placing the probe onto the tissue in gentle, stable contact. Tissue specimens were sampled for histopathological correlation.
RESULTS: The esophagus, stomach, small and large intestine and meso, liver, pancreas and gall bladder were visualised in vivo at high resolution in n = 48 mice. Real time microscopic imaging with the confocal mini-microscopy probe was easy to achieve. The different staining protocols (fluorescein, acriflavine, FITC-labelled dextran and L. esculentum lectin) each highlighted specific aspects of the tissue, and in vivo imaging correlated excellently with conventional histology. In vivo blood flow monitoring added a functional quality to morphologic imaging.
CONCLUSION: Confocal microscopy is feasible in vivo allowing the visualisation of the complete GI tract at high resolution even of subsurface tissue structures. The new confocal probe design evaluated in this study is compatible with laparoscopy and significantly expands the field of possible applications to intra-abdominal organs. It allows immediate testing of new in vivo staining and application options and therefore permits rapid transfer from animal studies to clinical use in patients.