Capsule OCT Endomicroscopy

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A team from Massachusetts General Hospital (MGH) has developed a tethered endomicroscopy capsule, offering a potential alternative to endoscopic tissue biopsy. It uses optical coherence tomography (OCT) to generate high-resolution cross-sections through the walls of the oesophagus. Capsules are already in use for video endoscopy, and OCT has been shown to have value in the diagnosis of Barrett’s oesophagus, but this is the first time the two technologies have been combined.

The capsule, which was described in Nature Medicine1, is built around a Fourier Domain OCT system. The imaging principle is essentially the same as for side-viewing OCT catheters: light from a single-mode fibre is deflected 90 degrees by a prism, giving a single depth scan through the tissue. Rotation of the fibre through 360 degrees produces a circular scan, while moving the fibre axially generates a 3D ‘tunnel’. The difference here is that, rather than being incorporated into a catheter, the tip of the fibre in inside a 13 x 25 mm capsule. The fibre runs out of the patient inside a 0.96 mm diameter sheath, which doubles as the ‘tether’ for the capsule.

After it’s swallowed, the capsule is naturally forced downwards by the luminal organs. The capsule is recovered by pulling on the tether, and it can then be sterilized for re-use. Imaging takes place both on the way down and on the way up, although the upwards motion will presumably tend to be more controlled. Unlike for conventional endoscopy there’s no need to sedate the patient, and the whole procedure, including four passes of the capsule, takes only six minutes. Another advantages is that, since the device doesn’t have to be steered, there’s less of a need for a highly trained operator.

The team tested their device on 13 patients, six of whom were known to have Barrett’s oesophagus. Normal and Barrett’s oesophagus can clearly be differentiated in the images shown in the paper, although the diagnostic accuracy of the device wasn’t assessed. When asked immediately afterwards, twelve of the patients claimed they preferred the capsule endomicroscopy to conventional endoscopy. While this isn’t the most rigorous of assessments, it does at least suggest the procedure isn’t horrific.

The technology has been patented and licensed to Ninepoint Medical. Rotating fibre systems for OCT catheters are already on the market, as are capsule endoscopes, so there shouldn’t be any huge practical problems in developing a viable product. Whether the device has a future will depend on how accurately diagnoses can be made from these kinds of images.

  1. Gora, Michalina J., et al. “Tethered capsule endomicroscopy enables less invasive imaging of gastrointestinal tract microstructure.” Nature medicine 19.2 (2013): 238-240.

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