□ Fig. 4.5a,b. Positioning of the confocal microscope. a The confocal microscope is visible at the left lower corner of the white-light endoscopic image (arrow). The area of interest has to be targeted with the endomicroscope. b Confocal images represent the tissue touched with the microscope. Sometimes continuous suction is mandatory to achieve full contact with tissue over the whole confocal microscopic window. A stable position is mandatory if an optical biopsy (confocal images from the surface and deeper parts of the tissue) is to be obtained

Conventional histology: Transverse section

i* t, * mm

  • ij <1W|STi>; - t- .v. " - 'll i;?
  • Fig. 4.6. In conventional histopathology, the specimen is cut into thin transverse slices, yielding a transverse section through the biopsies (left: H & E stain of normal colonic mucosa). Confocal endomi-croscopy results in an optical section that runs parallel to the tissue surface, corresponding to an en face view onto the mucosa (right, upper panel: H & E stain of normal colonic mucosa, lower panel: topcial acriflavine). (Schematicdiagram courtesy of Optiscan Pty, Ltd, Australia)

In vivo confocal microscopy: en face fiew

generated images to take advantage of in vivo histology during the ongoing examination. Interpretation of the confocal images requires a thorough knowledge of the normal and abnormal microscopic architecture of the upper and lower gastrointestinal tract; with pattern recognition rather than a minute appreciation of every subtle cellular detail common for early interpretation of normal and abnormal confocal imaging. To this end, confocal pattern classification systems have been established for the upper and lower gastrointestinal tract. They are based on the evaluation of the microvascular and crypt or glandular architecture, which are described in detail in the following chapters. The classification systems are easy to learn, easy to apply, allow an accurate and fast tissue diagnosis, and show good inter- and intra-observer agreement. Imaging depth of the currently used instruments is limited to 250 |im. Therefore, only the mucosa can be scanned while the submucosal layer cannot regularly be visualised. While learning confocal endomicroscopy (cf. ► Chap. 5), close collaboration with an expert gastrointestinal histopathologist should be sought for feedback on image interpretation. The possibility of simultaneous image interpretation and collabo

O Fig. 4.7. Superficial optical sections through normal colon mucosa. Left panel: Topical application of acriflavine hydrochloride stains nuclei of colonic goblet cells and absorptive cells around the crypt opening (arrowheads). Goblet cells can be identified by the bottle-neck opening

ration with histopathology may even be achieved using modern telecommunication systems.

Time requirements for confocal imaging have been studied in a prospective trial for colonoscopy. By adding both confocal endomicroscopy and chromoendoscopy to videoendoscopy, total examination time increased from an average of 31 min to 42 min in surveillance of patients with longstanding ulcerative colitis [1]. As with every examination technique, time requirements for confocal endomicroscopy are highly dependent on the expert status of the endoscopist.

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