Confocal laser endomicroscopy (CLE) is a new endoscopic modality developed to obtain very high-resolution images of the mucosal layer of the GI tract. CLE is based on tissue illumination with a low-power laser with subsequent detection of the fluorescence light reflected from the tissue through a pinhole. The term confocal refers to the alignment of both illumination and collection systems in the same focal plane. The laser light is focused at a selected depth in the tissue of interest and reflected light is then refocused onto the detection system by the same lens. Only returning light refocused through the pinhole is detected. The light reflected and scattered at other geometric angles from the illuminated object or refocused out of plane with the pinhole is excluded from detection. (1)
CLE is one of several novel methods that provide real-time, high-resolution imaging at a micronscale via endoscopes. CLE and similar technologies are often termed “virtual biopsy” as they are noted to mimic the images seen in conventional histology. However, the imaging of living tissue allows more than just practical convenience; it also permits imaging of living tissue such as active capillary circulation, cellular death, and vascular and endothelial translocation, thus extending beyond what is capable in traditional biopsy. Immediate potential applications of CLE are to guide biopsy sampling in Barrett’s esophagus and inflammatory bowel disease surveillance, evaluation of colorectal polyps, and intraductal imaging of the pancreas and bile duct. (2)
At least two CLE systems have received FDA clearance. According to the U.S. Food and Drug Administration (FDA) pre-market summary letter (K042740), "the Pentax Confocal Laser System is a required accessory for legally marketed video endoscopes equipped with a confocal laser imaging module. The system is intended to allow confocal laser imaging of the internal microstructure of tissues in the anatomical track assessed by the endoscope." The FDA premarket notification letter (K061666) for the F-600 System (Cellvizio® Confocal Miniprobe™) indicates this device is a "confocal laser system that is intended to allow confocal laser imaging of the internal microstructure of tissues in the anatomical tract, i.e., GI or respiratory, accessed by the endoscope."