Now consider extending the 5x5 dose plane to a 5 plane study. The 3 center planes are the same as before. The two end planes have 0% dose. Thus, we have a simple 3x3x3 volume of 100% dose, with 0% dose outside. The structure is now defined by the 3 contours (in yellow) that each exactly bound the 3x3 100% dose pixels. |