Characterizing muscle components in intestinal strictures using spectroscopic photoacoustic imaging

Inflammatory bowel disease (IBD) is a chronic autoimmune disease that causes obstructive intestinal strictures, characterized by inflammation, fibrosis, and muscular hypertrophy. Accurately characterizing the stricture pathology for therapeutic planning remains challenging. In our previous study, using multispectral photoacoustic (PA) imaging, we investigated the feasibility of quantifying the hemoglobin (Hb) and collagen components, corresponding to the inflammation and fibrosis, respectively, in animals in vivo and human subjects. In this study, we continued to investigate resolving the myoglobin (Mb) component that is associated with muscular hypertrophy. We validated the feasibility of quantitative PA imaging of the myoglobin (Mb) with imaging phantoms, and porcine and human tissue samples. We were able to visualize the distribution of the tissue components in porcine tissue samples ex vivo. Our study also revealed increased myoglobin and collagen content (n = 7, p < 0.01) in human intestinal strictures compared to the unstrictured margin. In addition, by employing argon plasma coagulation (APC), we generated a rabbit model with coexisting inflammation, fibrosis, and rich muscle tissue components. PA imaging results show that PA imaging is a promising tool to quantitatively evaluate the tissue components in intestinal strictures.