A prospective randomized study of two endo-knives for endoscopic submucosal dissection of colorectal neoplasm.

Interventions: Enrolled patients are enforced which groups of diveces Mucosectom2 group or SB knife Jr. at random.
Enrolled patients are enforced which groups of physician Y.S. or D.T. at random.
To allocate the size of the tumor can be stratified into 20-35mm and 36-50mm.
Primary outcome(s): Procedure time required for submucosal dissection of Mucosectom2 and SB knife. (The time is combined process of injection under the mucosa, of circular mucosal incision and of dissection of submucosa.)
Study Design: Parallel Randomized