Tethered capsule en face optical coherence tomography for imaging Barrett's oesophagus in unsedated patients

Abstract

Objective: Barrett's oesophagus (BE) screening outside the endoscopy suite can identify patients for surveillance and reduce mortality. Tethered capsule optical coherence tomography (OCT) can volumetrically image oesophageal mucosa in unsedated patients and detect features of BE. We investigated ultrahigh-speed tethered capsule swept-source OCT (SS-OCT), improved device design, developed procedural techniques and measured capsule contact, longitudinal pullback non-uniformity and patient toleration.

Design: OCT was performed in 16 patients prior to endoscopic surveillance/treatment. Unsedated patients swallowed the capsule with sips of water and the tether was pulled back to image the oesophagus. SS-OCT at 1 000 000 A-scans/s enabled imaging 10 cm oesophageal lengths in 10 s with 30 µm transverse and 8 µm axial resolution. Capsule contact, longitudinal image coverage and patient toleration were assessed.

Results: Nine patients had non-dysplastic BE, three had ablative treatment-naïve neoplasia and four had prior ablation for dysplasia. Dry swallows facilitated capsule transit through the lower oesophageal sphincter (LES), and waiting 10 s before pullback reduced swallow induced LES relaxation. Slow nasal inhalation facilitated capsule retrieval and minimised gag reflex. The procedure was well tolerated. Ultrahigh-speed SS-OCT generated cross-sectional and subsurface en face images showing BE features, while subsurface en face images were required to assess the gastro-oesophageal junction. Candidate features of dysplasia were also identified which could inform follow-up endoscopy/biopsy. BE features were seen in all patients with histologically confirmed BE. Mean capsule contact over BE was 75%±27% for all patients and better in short segment BE. Mean longitudinal image coverage over BE was 59%±34% and better for long segment BE.

Conclusions: Ultrahigh-speed tethered capsule SS-OCT can image en face and cross-sectional mucosal features over wide areas. Device and procedure optimisation improved performance. BE features could be identified in all patients, but limited capsule contact and longitudinal coverage could cause sampling errors for focal pathologies.

Keywords: Barrett's oesophagus; imaging; screening; surveillance.

Figure 1

(A) Photograph of tethered optical coherence tomography (OCT) capsule constructed using lubricious material with a 30° proximal taper for ease of retrieval. (B) Tether markings every 5 cm indicating distance from incisors. (C) Schematic showing micromotor rotary optical scanner and other components. (D) Cartoon showing capsule travelling from gastric cardia into distal oesophagus during a pullback image acquisition. (E) Illustration showing multiple cross-sectional images acquired in rapid succession during capsule pullback to obtain volumetric data for subsurface en face and cross-sectional visualisation.

Figure 2

Box plots of tissue contact and longitudinal capsule motion uniformity/coverage over the en face Barrett’s oesophagus (BE) region in the tethered capsule optical coherence tomography (OCT) datasets. Coloured circles indicate individual data points. Tissue contact was significantly different (*) between short/long segment BE (SSBE, LSBE) (p=0.03) and absence/presence of sliding hiatal hernia (HH) (p=0.04).

Figure 3

Preprocedure anxiety and procedural discomfort scores for the tethered capsule and endoscopy procedures. 1, no anxiety/discomfort, 5, high anxiety/discomfort. Scores between patient subgroups of baseline pathology and treatment history were similar. NDBE, non-dysplastic Barrett’s oesophagus.

Figure 4

Tethered capsule optical coherence tomography (OCT) from a patient with C2M4 non-dysplastic Barrett’s oesophagus (BE). Inset shows narrow band imaging view from a previous endoscopy. (A) En face OCT at 200 µm depth, (B) 400 µm depth and (C) full depth projection. Scale bars 1 cm. Some longitudinal pullback non-uniformity can be observed in the BE segment. (D–F) Enlargements showing glands and mucosal pattern at the gastro-oesophageal junction (GEJ). Scale bars 1 mm. (G) Cross-sectional OCT from the GEJ showing atypical glands. Scale bar 500 µm. Biopsy at the GEJ (inset) from a prior oesophagogastroduodenoscopy (9 months earlier) shows a large dilated cardiac gland (arrow) with smaller peripheral glands from the superficial mucosa.