Incorporating interfractional motion in the treatment planning for motion compensated radiosurgery

In robotic radiosurgery cyclic movements of the target, like respiratory motion, can be compensated by moving the beams accordingly. However, conventionally treatment planning is performed on 3D image data and does not account for organ motion. We propose to discretize the target motion into steps along its spatial dimensions. For each step we compute its fraction of the breathing cycle, calculate the dose coefficient and incorporate this information in the optimization phase of the planning problem. Simulating planning and dose delivery for a simplified test case we show that the new approach can mitigate potential problems when treating highly mobile targets with motion compensated radiosurgery.