A3) During 4D radiotherapy (4DRT) delivery the tumor is continuously tracked with the radiation beam as they move throughout the respiratory cycle. The benefits of 4DRT are a reduction in dose to the healthy lung tissue and/or an increase in dose to the tumor. The gains from 4DRT are clinically measurable, though much development is needed in the various steps of 4DRT i.e. CT image acquisition, planning and delivery.