Figure 2 The introduction of EUS elastography image (A) and hue mean histogram (B). The image shows the EUS and EUS elastography of a patient with gastrointestinal stromal tumor in stomach. Figure A the left part is an EUS image, on which we can see 5 layers of the gastric tract wall, lined mucosa, muscularis mucosa, submucosa, muscularis propria, and serosa from inside to outside, and the focus sited in the layer of muscularis propria. Figure A the right part is an EUS elastography image, which is superimposed by colors of blue (hard tissues), green (intermedium tissues), and red (soft tissues) according to different elasticity produced by different tissues. The bottom-left corner is the appearance of electronic endoscopy. Figure B this picture shows the mean hue histogram of an area we selected (ROI). There were 4 channels: the front-most is the RGB channel, which was mixed by following 3 channels of R channel, G channel, and B channel. Each image shows the mean value and SEM; for example, 71.29 and 34.02 of RGB channel in this picture. Simultaneously, we obtained mean values of separated channels of R, G, and B respectively.