1. A medical diagnosis apparatus comprising: a scanner configured to scan a three-dimensional region including a target region and acquire data of the three-dimensional region: processing circuitry configured to: discretely arrange fixed points framing three-dimensional shape of the target region in a first medical image based on the data; set a boundary of region of interest (ROI) on the three-dimensional shape of the target region according to a position of the fixed point; receive an instruction to change a position of the boundary from an input device controlled by a user; and change the position of the boundary based on a position or positions of at least one of the fixed points according to the instruction while maintaining positions of the fixed points.