Assessing intestinal fibrosis using an endoscopic photoacoustic-ultrasound balloon catheter in rabbits and a human subject.

Background and aims: Assessment of fibrosis in intestinal strictures in Crohn's disease could contribute to clinical decision making. Our recent studies demonstrate that endoscopic photoacoustic (PA) imaging can quantify the progression of intestinal fibrosis by its collagen content and its mechanical stiffness. The aim of this study is to evaluate the feasibility and diagnostic reliability of a PA-ultrasound balloon catheter in assessing intestinal fibrosis.

Methods: Acute colonic colitis or chronic inflammation with fibrosis was induced in rabbits using intrarectal trinitrobenzene sulfonic acid. The affected distal colon was assessed through PA imaging in vivo and microelastometry ex vivo. Quantitative measurements were derived from the images and compared with histopathology. We also examined the feasibility of the catheter in a human subject with Crohn's disease strictures.

Results: The quantitative PA imaging measurements in vivo detected an increased collagen/hemoglobin ratio of 1.42 arbitrary units (p < 0.001) in the chronic high fibrosis rabbit group compared to the acute colitis/low fibrosis and normal groups. The imaging results in vivo also showed an increased relative tissue stiffness of 4.27 KPa (p < 0.001) in the high fibrosis group compared to the low fibrosis and normal groups, which agrees with ex vivo microelastometer measurements. The human subject study demonstrates sufficient light penetration and signal-to-noise ratio for assessing intestinal fibrosis during a standard ileo-colonoscopy procedure.

Conclusion: Our novel imaging catheter shows reliability in differentiating the changes in molecular components and mechanical properties during the progression of intestinal fibrosis. This catheter-based approach is fully compatible with clinical colonoscopy procedures.