  Detection of Barrett's esophagus (BE) at points of care outside the endoscopy
suite may improve screening access and reduce esophageal adenocarcinoma
mortality. Tethered capsule optical coherence tomography (OCT) can
volumetrically image esophageal mucosa and detect BE in unsedated patients. We
investigated ultrahigh-speed tethered capsule, swept-source OCT (SS-OCT) in
unsedated patients, improved device design, developed procedural techniques,
measured how capsule contact and longitudinal pullback non-uniformity affect
coverage, and assessed patient toleration. OCT was performed in 16 patients
prior to endoscopic surveillance/treatment. Unsedated patients swallowed the
capsule with small sips of water and the esophagus imaged by retracting the
tether. Ultrahigh-speed SS-OCT at 1,000,000 A-scans/second imaged ~40cm$^2$
esophageal areas in 10 seconds with 30um transverse and 8um axial resolution.
Nine patients had non-dysplastic BE, 3 had ablative treatment-naive neoplasia,
and 4 had prior ablation for history of dysplasia. The capsule procedure was
well tolerated. Ultrahigh-speed SS-OCT enabled the generation of
cross-sectional and sub-surface en face images. BE could be rapidly identified
in cross-sectional and en face images, while assessment of the
gastro-esophageal junction (GEJ) required subsurface en face views. Capsule
esophageal contact was worse in long-segment BE and sliding hiatal hernia, and
longitudinal image coverage was worse in short-segment BE. OCT candidate
features of dysplasia are reported. Ultrahigh-speed tethered capsule SS-OCT
enabled en face and cross-sectional imaging of mucosal features over wide
areas. Device and procedure optimization led to improved imaging performance.
Areas of BE could be readily identified, but limited capsule contact and
longitudinal image coverage can yield sampling errors.
