Fig. 1. Photoacoustic endoscopic imaging probe and system. (a) Schematic of photoacoustic imaging system; (b) schematic of spiral scanning and imaging; (c) structural diagram of endoscopic probe; (d) cross sectional structure of endoscopic probe; (e) schematic of depth of field and imaging depth; (f) photo of endoscopic imaging system

Fig. 2. Imaging performance characterization of endoscopic probe. (a) Characterization method and (c) results of lateral spatial resolution; (b) characterization method and (d) results of stability

Fig. 3. Photoacoustic endoscopic imaging results of intestinal tract of healthy small animals. (a) Scanning diagram; (b) three dimensional distribution of blood vessels in inner wall of rectum; (c) 2D spatial distribution of normalized amplitude of photoacoustic signal; (d) 2D spatial distribution of blood oxygen saturation; (e) 2D spatial distribution of blood vessel depth

Fig. 4. Photoacoustic endoscopic imaging results of intestinal tract of healthy rat. (a) Normalized amplitude of photoacoustic signal; (b) blood oxygen saturation

Fig. 5. Imaging results of intestinal model in septic rats. (a) Normalized amplitude of photoacoustic signal; (b) blood oxygen saturation