Deriving New Structure

550px|right|thumb|GUI to derive new structures As name suggests, the purpose of this tool is to derive new structures based on the existing structures. For example: Deriving a structure (Skin - PTV) to be used for IMRTP. Image to the right shows this tool in action. The workflow for using this tool follows:

1> Invoke this tool from CERR menubar. Structures --> Derive new structure.

2> Select 'Operation' from the left panel. Various options are:

• Intersection: Creates a new structure which is intersection between the two selected structures.
• Subtraction: Creates a new structure subtraction between the 1st and 2nd selected structure.
• Union: Creates a new structure which is union of the two selected structures.
• Addition of 2D margin: Creates a new structure by adding a specified margin to selected structure. The margin is added on slice-by-slice basis, hence 2D.
• Subtraction of 2D margin: Creates a new structure by removing a specified margin from selected structure. The margin is removed on slice-by-slice basis, hence 2D.
• Addition of 3D margin: Creates a new structure by adding a specified margin to selected structure. The margin is added to binary 3D volume representation of the structure, hence 3D.
• Subtraction of 3D margin: Creates a new structure by removing a specified margin from selected structure. The margin is removed from binary 3D volume representation of the structure, hence 3D.
• Filling Slice-gaps: Creates a new structure by interpolating contours to 'in-between' slices. The 'in-between' slices are ones which are not contoured, but lie in between the contoured slices.

3> Select Structure/s to operate on from the middle panel.

4> Hit the 'Make Intermediate' button once the existing structures have been selected.

5> Hit the 'Make Struct' button followed by the intermediate structure to be derived.

Note that only the structures associated to the same scan can be combined together.