Underwater ESD vs Conventional ESD for SCN

Interventions: Procedure/Surgery : underwater endoscopic submucosal dissection - after submucosal injection, partial circumferential submucosal incision around the superficial colorectal neoplasia, and then conducted submucosal dissection with water pressure assisted traction on underwater conventional endoscopic submucosal dissection - after submucosal injection, partial circumferential submucosal incision around the superficial colorectal neoplasia, and then conducted submucosal dissection Primary outcome(s): procedure time (measured as the time from the submucosal injection to complete removal of the superficial colorectal neoplasia based on endoscopic assessment) Primary Purpose : Treatment, Intervention Model : Parallel, Blinding/Masking : , Blinding Target : Subject, Allocation : RCT