Mehul, It is difficult to tell from that one slice. Is that wm excluded in the next slices adjacent to that slice? You are putting control points in very thin areas there. It might be best to put them in areas within the surface (close to the areas being excluded) - check what the intensity value is at that voxel (a control point will only help if it's less than 110) and don't put them on wm voxels neighboring gm voxels.