A feasibility study of photoacoustic imaging of ex vivo endoscopic mucosal resection tissues from Barrett’s esophagus patients

Background and study aims Accurate endoscopic detec- tion 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 gui- dance, but this leaves the majority of the tissue unsampled, leading to significant risk of missing dysplasia. Further- more, determining whether there is submucosal invasion is essential for proper staging. Hence, there is a clinical need forarapidin vivowide-fieldimaging 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 microvas- cular pattern, with the long-term goal of performing in vivo endoscopic PAI for dysplasia detection and therapeutic gui- dance. Materials and methods EMR tissues were mounted lumi- nal side up.The tissues were scanned over a field of view of 14mm (width) by 15mm (depth) at 680, 750, and 850nm (40MHz acoustic central frequency). Ultrasound and pho- toacoustic images were simultaneously acquired. Tissues were then sliced and fixed in formalin for histopathology with hematoxylin and eosin staining. A total of 13 EMR spe- cimens from eight patients were included in the analysis, which consisted of co-registration of the photoacoustic images with corresponding pathologist-classified histologi- cal images.We conducted mean difference test of the total hemoglobin distribution between tissue classes. Results Dysplastic and nondysplastic BE can be distin- guished 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 im- portant 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 exo- genous contrast) can differentiate BE from squamous esophageal mucosa. However,most likely intrinsic PAI is un- able to differentiate dysplastic from nondysplastic BE with adequate sensitivity for clinical translation.