Comprehensive esophageal microscopy by using optical frequency-domain imaging (with video)

Abstract

Background: Optical coherence tomography (OCT) has been used for high-resolution endoscopic imaging and diagnosis of specialized intestinal metaplasia, dysplasia, and intramucosal carcinoma of the esophagus. However, the relatively slow image-acquisition rate of the present OCT systems inhibits wide-field imaging and limits the clinical utility of OCT for diagnostic imaging in patients with Barrett's esophagus.

Objective: This study describes a new optical imaging technology, optical frequency-domain imaging (OFDI), derived from OCT, that enables comprehensive imaging of large esophageal segments with microscopic resolution.

Design: A prototype OFDI system was developed for endoscopic imaging. The system was used in combination with a balloon-centering catheter to comprehensively image the distal esophagus in swine.

Results: Volumetric images of the mucosa and portions of the muscularis propria were obtained for 4.5-cm-long segments. Image resolution was 7 microm in depth and 30 microm parallel to the lumen, and provided clear delineation of each mucosal layer. The 3-dimensional data sets were used to create cross-sectional microscopic images, as well as vascular maps of the esophagus. Submucosal vessels and capillaries were visualized by using Doppler-flow processing.

Conclusions: Comprehensive microscopic imaging of the distal esophagus in vivo by using OFDI is feasible. The unique capabilities of this technology for obtaining detailed information of tissue microstructure over large mucosal areas may open up new possibilities for improving the management of patients with Barrett's esophagus.

Figure 1

The OFDI system schematic.

Figure 2

The imaging catheter and balloon centration mechanism is shown. A, The limited field of view of the conventional catheter. B, The use of a balloon-centering catheter that allows full circumferential imaging overcomes the limited field of view of conventional catheter. C, The balloon catheter is shown schematically.

Figure 3

OFDI images of the distal esophagus. The esophageal circumference in all figures is given by the balloon circumference (56 mm). A, Three-dimensional renderings of the distal esophagus with quadrant cut-outs and planes designating the locations of the cross-sectional images. B, A trans-verse cross-sectional image; the balloon appears as the inner surface and is clearly apparent in the lower portion of the image where an air/mucus pocket separates the balloon and luminal wall; the radial depth scale is given by the indicated scale bar. The images in (A) and (B) are presented with distorted dimensions to allow for greater visualization of detail. C, A longitudinal cross-sectional image is shown (arrows designating residual motion artifacts); note that the 3-dimensional images use an inverted reflectivity mapping (white corresponds to higher reflectivities) to improve visualization.

Figure 4

A, A transverse cross-sectional image showing all architectural layers of the squamous mucosa, including the epithelium (e), lamina propria (lp), muscularis mucosa (mm), submucosa (sm), and muscularis propria (mp); because of the large change in esophageal circumference during imaging (56 mm) and after resection (~22 mm), the cross-sectional image is displayed over a proportionately larger width. B, Representative histology from the same swine (H&E, orig. mag. ×2).

Figure 5

Imaging of the SCJ. A, Three-dimensional renderings of the SCJ are shown, with planes designating locations of the cross-sectional images. B and C, Unwrapped transverse cross-sectional images spanning 360°. D, Representative histology of (E) (H&E, orig. mag. ×2). E, A longitudinal cross-sectional image; the depth of the muscularis mucosa is observed to vary significantly at the transformation zone (black arrows); residual motion artifacts are indicated by the white arrow. A supplementary video representing a full-volume pull-back sequence is available at www.giejournal.org.

Figure 6

A, A comprehensive vascular map derived from the structural image set. B to D, Cross-sectional images at the indicated locations. Arrows indicate corresponding vessels in the vascular map and cross-sectional images.

Figure 7

A vascular map, including Doppler signal processing. A, The Doppler signal magnitude is displayed by using the indicated color lookup table and overlaid on a structural image. B and C, Cross-sectional images from locations designated in (A).