Crohn’s disease (CD) is a chronic autoimmune disease of the intestinal tract affecting 700,000 people in the United States. The pathology of CD is characterized by obstructing intestinal strictures due to inflammation (with high levels of hemoglobin), fibrosis (with high levels of collagen), or a combination of both. The accurate characterization of the intestinal strictures is critical, as the fibrotic intestinal strictures have to be removed surgically. Currently, there is no imaging modality that can differentiate the fibrotic and inflammatory strictures. Standard diagnosis by endoscopic biopsy suffers from the post-procedure complications, and limited sampling locations and depth.
Combining the optical spectroscopy and ultrasound (US) imaging, photoacoustic (PA) imaging is an ideal tool for resolving the molecular components of the intestinal strictures. This study investigates the feasibility of differentiating the fibrotic and inflammatory intestinal strictures using PA-US parallel imaging in a rat model in vivo. A linear US array was used to acquire US and PA imaging transcutaneously. PA imaging with endoscopic and transcutaneous illumination was attempted in 12 and 10 animals, respectively. The PA images were acquired at 750, 850 and 1310 nm. The PA pixel intensities within the intestinal stricture regions were quantified. Blood oxygenation, as well as the relative ratio between the total hemoglobin and collagen contents, were derived. Significant differences were observed between the fibrotic and inflammatory strictures (p<0.05). The penetration of the noninvasive transcutaneous PA imaging was also tested in human subjects using a low-frequency probe. Penetration as deep as 6 cm was achieved.
Yunhao Zhu, Laura Johnson, Jonathan Rubin, Xueding Wang, Peter Higgins, and Guan Xu, "Characterization of intestinal fibrosis and inflammation with transcutaneous spectroscopic PA imaging (Conference Presentation)," Proc. SPIE 10494, Photons Plus Ultrasound: Imaging and Sensing 2018, 104941L (Presented at SPIE BiOS: January 30, 2018; Published: 15 March 2018); https://doi.org/10.1117/12.2287983.5752200782001.
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