Creating geometry from boundary points in MATLAB

Hi everyone, I am working on 2D MRI data which is square. However the information is included in another shape (head, foot etc.). So I need to create mesh of that shape. I used edge detection and boundarytrace to find detect boundary points of the shape. Now I have the boundary points as (nxn) logical matrix as well as [x y] coordinates. I searched for mesh creating and I think I need to use initmesh function. However I cannot seem to find how to create geometry.

Can you help me with this? Any tips will be welcomed.