Patent Number: 
Section: claims

1. An ion therapy machine comprising:an ion source for producing an ion beam traveling along an axis;means for varying a lateral width of the ion beam perpendicular to the axis as a function of a control signal;means for varying an axial extent of the beams when steered to portions of the patient according to a control signal;means for steering a center of the ion beam to different portions of a patient according in both lateral and axial dimensions to a control signal; anda beam controller executing a stored radiation plan to communicate control signals to the means for varying a lateral width, the means for varying an axial extent and the means for steering the ion beam, to provide a radiation treatment to the patient by applying ion beams of different widths to different portions of the patient. 2. The ion therapy machine of claim 1 further including:apparatus for rotating the axis of the ion beam to different angles with respect to the patient; andwherein the beam controller further executes the stored radiation plan to communicate control signals to the means for varying an axial extent, the means for varying the lateral width and steering means to apply ion beams with higher gradients at the distal edge of the tumor than at a center of the tumor. 3. The ion therapy machine of claim 1 wherein the means for varying a lateral width is a pair of successive quadrupole magnets and the width of the ion beam is adjusted by varying a separation of the quadrupole magnets. 4. The ion therapy machine of claim 1 wherein the means for varying an axial extent is a set of selectable mechanical ridge filters. 5. The ion therapy machine of claim 1 wherein the means for varying a lateral width is a mechanical collimator. 6. The ion therapy machine of claim 1 further including a radiation planning system receiving a dose plan for a tumor within the patient and providing the radiation plan to the beam controller such that the radiation plan applies wider beams to portions of the tumor with higher gradients of the dose plan and narrower beams to portions of the tumor with lower dose gradients of the dose plan in regions removed from edges of the tumor. 7. The ion therapy machine of claim 1 further including a radiation planning system receiving a dose plan for the patient and providing the radiation plan to the beam controller to steer the beams to place Bragg peaks of the beams at distal edges of a tumor. 8. A method of radiation treatment with an ion beam traveling along an axis comprising the steps of:executing a stored radiation treatment plan to:(a) vary a lateral width of the ion beam perpendicular to the axis according to beam width data in the radiation treatment plan;(b) vary an axial extent of the ion beam along the axis according to beam extent data in the radiation treatment plan;(c) steer the axis of the ion beam to different portions of a patient according to beam location data in the radiation treatment plan;whereby ion beams of different widths and extents are applied to at least two different portions of the patient.