Interplay effect in lung cancer proton therapy

Pencil beam scanning proton therapy is used increasingly for cancer treatment. Although this technique allows superior dose avoidance to critical organs in comparison to passive scattering and X-rays photon-type radiation therapy, it is more susceptible to changes in the patient’s inherent anatomical motion, especially in the thoracic region. The uncertainties in dose distribution due to motion interplay in this region are significant and cannot be ignored. This paper focuses on the errors in dose delivery when motion interplay is involved, and how we can quantify them practically. With the proper tools for evaluating the magnitude of such errors, the best method to mitigate motion effects can be decided and designed for each individual patient.