Comparison between the five submucosal simulated tumors. (a) Photo image of gastric sample; (b) Photographs of five submucosal simulated tumors under endoscope; (c) Optical fiber under endoscopy; (d) Photo image of gastric wall; (e) Real-time 2D US image of simulated tumor ID 5; (f) Real-time 2D PA image of simulated tumor ID 5; (g) Real-time 2D photoacoustic and ultrasonic dual-mode imaging of simulated tumor ID 5; (h) Normalized mean optical absorption and PA intensity of five submucosal simulated tumors; (i) Structure information and infiltration depth of five submucosal simulated tumors; (j) SNR and contrast degree for 2D PA and US images of five submucosal simulated tumors.