Target Volume Determination 2015

Keeping things in perspective

• GTV  PTV margin – All cells in the GTV are considered to be tumor – P underdosage = P geometrical miss – Use margin prescription • CTV  PTV margin – In the CTV there is a probability of tumor cells – P underdosage = P geometrical miss x P presence of tumor cells – Margin can probably be smaller

• Caveat: Tumor cell probability is needed