Abstract
Background and study aims Accurate endoscopic detection of dysplasia in patients with Barrett’s esophagus (BE)
remains a major clinical challenge. The current standard is to take multiple biopsies
under endoscopic image guidance, but this leaves the majority of the tissue unsampled,
leading to significant risk of missing dysplasia. Furthermore, determining whether
there is submucosal invasion is essential for proper staging. Hence, there is a clinical
need for a rapid in vivo wide-field imaging method to identify dysplasia in BE, with
the capability of imaging beyond the mucosal layer. We conducted an ex vivo feasibility
study using photoacoustic imaging (PAI) in patients undergoing endoscopic mucosal
resection (EMR) for known dysplasia. The objective was to characterize the esophageal
microvascular pattern, with the long-term goal of performing in vivo endoscopic PAI
for dysplasia detection and therapeutic guidance.
Materials and methods EMR tissues were mounted luminal side up. The tissues were scanned over a field of
view of 14 mm (width) by 15 mm (depth) at 680, 750, and 850 nm (40 MHz acoustic central
frequency). Ultrasound and photoacoustic images were simultaneously acquired. Tissues
were then sliced and fixed in formalin for histopathology with hematoxylin and eosin
staining. A total of 13 EMR specimens from eight patients were included in the analysis,
which consisted of co-registration of the photoacoustic images with corresponding
pathologist-classified histological images. We conducted mean difference test of the
total hemoglobin distribution between tissue classes.
Results Dysplastic and nondysplastic BE can be distinguished from squamous tissue in 84 %
of region-of-interest comparisons (42/50). However, the ability of intrinsic PAI to
distinguish dysplasia from NDBE, which is the clinically important challenge, was
only about 33 % (10/30).
Conclusion We demonstrated the technical feasibility of this approach. Based on our ex vivo
data, changes in total hemoglobin content from intrinsic PAI (i. e. without exogenous
contrast) can differentiate BE from squamous esophageal mucosa. However, most likely
intrinsic PAI is unable to differentiate dysplastic from nondysplastic BE with adequate
sensitivity for clinical translation.
