Optical coherence tomography-guided laser marking with tethered capsule endomicroscopy in unsedated patients

Abstract

Tethered capsule endomicroscopy (TCE) is an emerging screening technology that comprehensively obtains microstructural OCT images of the gastrointestinal (GI) tract in unsedated patients. To advance clinical adoption of this imaging technique, it will be important to validate TCE images with co-localized histology, the current diagnostic gold standard. One method for co-localizing OCT images with histology is image-targeted laser marking, which has previously been implemented using a driveshaft-based, balloon OCT catheter, deployed during endoscopy. In this paper, we present a TCE device that scans and targets the imaging beam using a low-cost stepper motor that is integrated inside the capsule. In combination with a 4-laser-diode, high power 1430/1450 nm marking laser system (800 mW on the sample and 1s pulse duration), this technology generated clearly visible marks, with a spatial targeting accuracy of better than 0.5 mm. A laser safety study was done on swine esophagus ex vivo, showing that these exposure parameters did not alter the submucosa, with a large, 4-5x safety margin. The technology was demonstrated in living human subjects and shown to be effective for co-localizing OCT TCE images to biopsies obtained during subsequent endoscopy.

Volumetric Laser Endomicroscopy in Barrett's Esophagus

“…Early TCE studies showed feasibility without significant adverse events 13,14 . The recent addition of a laser marking system should allow studies to evaluate for histopathologic correlation to TCE images 15 . Currently, this technology is not commercially available.…”

Application of OCT in the Gastrointestinal Tract

“…A capsule in 2015 was able to combine en face and circumferential luminal scanning to obtain large field coverage (30 cm2) and small field inspection (1 cm2), yielding both volumetric and en face imaging [124]. A more recent capsule paper [131] also incorporated laser marking into tethered capsule endomicroscopy (TCE). Laser marking is a way of co-localizing OCT images with histology [131] (120), and the laser marks had a spatial accuracy of better than 0.5 mm.…”

“…A more recent capsule paper [131] also incorporated laser marking into tethered capsule endomicroscopy (TCE). Laser marking is a way of co-localizing OCT images with histology [131] (120), and the laser marks had a spatial accuracy of better than 0.5 mm. However, small diameter probes sacrifice FOV for transverse resolution, which is a potential drawback of en face capsule technology [124].…”

Shadow-free motorized capsule enables accurate beam positioning and sectorized OCT imaging of the esophagus

“…3,4 A distal motorized design allows for a reduced rotational distortion, accurate beam scanning, 5,6 and laser marking procedures. 7 However, wires of distal motors partially block the scanning area, producing image shadows. This issue might become critical when abnormal tissue is coincidentally blocked in the image.…”