Methods and apparatus for the planning and delivery of radiation treatments

A method for delivering radiation dose to a target area within a subject, the method comprising:

• defining a trajectory comprising relative movement between a treatment radiation source and the subject and determining a radiation delivery plan;
• while effecting relative movement between the treatment radiation source and the subject along the trajectory, delivering a treatment radiation beam from the treatment radiation source to the subject according to the radiation delivery plan to impart a dose distribution on the subject, wherein delivering the treatment radiation beam from the treatment radiation source to the subject comprises varying at least one of an intensity of the treatment radiation beam and a shape of the treatment radiation beam over at least a portion of the trajectory;
• while effecting relative movement between the treatment radiation source and the subject along the trajectory, obtaining two-dimensional projection images of the target area at a plurality of locations along the trajectory;
• and
• wherein varying the intensity of the treatment radiation beam over at least a portion of the trajectory comprises varying a radiation output rate of the treatment radiation source in accordance with the radiation delivery plan while effecting relative movement between the treatment radiation source and the subject along the trajectory.