A computer-implemented method of determining a treatment field trajectory for a radiation treatment of a patient, the method comprising: receiving a radiation treatment plan, the radiation treatment plan including a plurality of treatment fields of an IMRT modality and a dynamic treatment path modality, each treatment field defining one or more spatial points for delivering a respective portion of a desired dose, each spatial point defining a respective set of values for treatment axes of a radiation treatment system; characterised by the following steps: identifying, using a computer system, a plurality of candidate treatment trajectories by analyzing the respective set of values for the treatment axes of each spatial point associated with the plurality of treatment fields, each candidate treatment field trajectory comprising a chronological order of administering the plurality of treatment fields, including interleaving the plurality of treatment fields; for each of the plurality of candidate treatment trajectories: determining, using the computer system, a total treatment time including beam-on time when radiation dose is being delivered and beam-off time during transitioning of the treatment axes between consecutive treatment fields; selecting, using the computer system, an optimal treatment field trajectory among the plurality of candidate treatment trajectories to achieve an optimal total treatment time; and updating the radiation treatment plan using the optimal treatment field trajectory. receiving a radiation treatment plan, the radiation treatment plan including a plurality of treatment fields of an IMRT modality and a dynamic treatment path modality, each treatment field defining one or more spatial points for delivering a respective portion of a desired dose, each spatial point defining a respective set of values for treatment axes of a radiation treatment system; characterised by the following steps: identifying, using a computer system, a plurality of candidate treatment trajectories by analyzing the respective set of values for the treatment axes of each spatial point associated with the plurality of treatment fields, each candidate treatment field trajectory comprising a chronological order of administering the plurality of treatment fields, including interleaving the plurality of treatment fields; for each of the plurality of candidate treatment trajectories: determining, using the computer system, a total treatment time including beam-on time when radiation dose is being delivered and beam-off time during transitioning of the treatment axes between consecutive treatment fields; selecting, using the computer system, an optimal treatment field trajectory among the plurality of candidate treatment trajectories to achieve an optimal total treatment time; and updating the radiation treatment plan using the optimal treatment field trajectory. identifying, using a computer system, a plurality of candidate treatment trajectories by analyzing the respective set of values for the treatment axes of each spatial point associated with the plurality of treatment fields, each candidate treatment field trajectory comprising a chronological order of administering the plurality of treatment fields, including interleaving the plurality of treatment fields; for each of the plurality of candidate treatment trajectories: determining, using the computer system, a total treatment time including beam-on time when radiation dose is being delivered and beam-off time during transitioning of the treatment axes between consecutive treatment fields; selecting, using the computer system, an optimal treatment field trajectory among the plurality of candidate treatment trajectories to achieve an optimal total treatment time; and updating the radiation treatment plan using the optimal treatment field trajectory. determining, using the computer system, a total treatment time including beam-on time when radiation dose is being delivered and beam-off time during transitioning of the treatment axes between consecutive treatment fields; selecting, using the computer system, an optimal treatment field trajectory among the plurality of candidate treatment trajectories to achieve an optimal total treatment time; and updating the radiation treatment plan using the optimal treatment field trajectory.