Abstract Background Gastrointestinal tract (GI) strictures are a major cause of morbidity and mortality in Crohn’s disease. Differentiating between inflammatory and fibrotic strictures is critical for effective clinical management as inflammatory strictures often respond to medical therapy, while fibrotic strictures typically require surgery. Current diagnostic tools fail to differentiate inflammatory from fibrotic strictures. To fill this diagnostic gap, we have developed a tunable laser photoacoustic (PA) and ultrasound (US) imaging catheter compatible with clinical endoscopes to measure tissue components of hemoglobin and collagen to differentiate between inflammatory and fibrotic strictures. Methods The PA-US imaging system and balloon catheter were adapted from our previous devices for compatibility with clinical endoscopes. A tunable side-firing laser was used to illuminate specific molecules (collagen, hemoglobin) to induce vibration at specific wavelengths. An ultrasound array was used to detect and measure molecular signals. Proof-of-concept in vivo imaging was performed using a pig esophageal fibrosis model. Baseline PA-US imaging was performed at multiple regions along the esophagus. Multiple fibrotic lesions were induced by superficial APC burn, interspersed with undamaged regions. PA-US imaging with endoscopy was performed at baseline and 2 weeks post APC. PA-US resolution of tissue hemoglobin and collagen was compared to histological inflammation and fibrosis. Results Significantly increased histological inflammation and fibrosis was observed in the APC lesions after healing vs. normal margin. No differences in either hemoglobin or collagen were observed by PA-US at baseline or in the untreated margins. PA-US imaging demonstrated a significant increase in both hemoglobin and collagen content in the healed lesions compared to either baseline or the normal margin. Conclusion This study presents a dual-modality photoacoustic and ultrasound imaging catheter compatible with standard clinical endoscopy. In a porcine model, the system detected changes in hemoglobin and collagen content associated with inflammation and fibrosis, with elevated collagen signals following APC treatment. We have successfully tested this endoscopic catheter in Crohn’s patients with terminal ileal strictures. This study supports the integration of spectroscopic PA-US imaging into GI workflows for noninvasive assessment of strictures for tissue fibrosis. Conflict of interest: Huang, Yaocai: No conflict of interest Johnson, Laura: No conflict of interest Peng, Xiaorui: No conflict of interest Lee, Yao: No conflict of interest Wang, Xueding: No conflict of interest Xu, Gary: No conflict of interest Higgins, Peter: Grant: NIH, Abbvie, Eli Lilly, Pfizer Personal Fees/Consulting - Abbvie Non-financial Support: None
Huang et al. (Thu,) studied this question.
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