Patent Number: 
Section: claims

1. A method to administer a planned total radiation dose according to a radiation treatment plan to a patient in a single radiation treatment session using a multi-leaf collimator comprised of a plurality of pairs of selectively movable collimating leaves, the method comprising:administering a sequential plurality of modulated radiation doses to the patient, where the sequential plurality of modulated radiation doses includes:at least one modulated radiation dose administered by modulating the radiation beam with the multi-leaf collimator using a sliding-window pattern to provide some of, but not more than twenty-five percent of, the planned total radiation dose; anda plurality of modulated radiation doses that are each administered while modulating a radiation beam with the multi-leaf collimator using a curtain pattern and wherein at least one of the plurality of pairs of selectively movable collimating leaves moves at a different speed than another of the pairs of selectively movable collimating leaves to provide a substantial majority of, but not all of, the planned total radiation dose. 2. The method of claim 1 wherein the curtain pattern comprises moving collimating leaves of the pairs of collimating leaves towards one another from an opened position. 3. The method of claim 1 wherein the curtain pattern comprises moving collimating leaves of the pairs of collimating leaves away from one another from a closed position. 4. The method of claim 1 further comprising:reducing a dose rate during a sub-sequence when moving collimating leaves following a completed curtain pattern to prepare to execute a follow-on curtain pattern. 5. The method of claim 4 wherein reducing the dose rate does not include shutting off the radiation beam. 6. The method of claim 4 wherein administering the sequential plurality of modulated radiation doses comprises administering the sequential plurality of modulation doses in a particular order of treatment that minimizes a total time required for all sub-sequences to move collimating leaves following a completed curtain pattern to prepare to execute a follow-on curtain pattern. 7. The method of claim 1 wherein the radiation treatment plan is formed by converting an arbitrary optimal fluence map into a plurality of curtain-pattern leaf trajectories for the multi-leaf collimator. 8. The method of claim 7 wherein the radiation treatment plan is further formed by using leaf transition sub-sequences between curtain-pattern leaf trajectories. 9. An apparatus to administer a planned total radiation dose according to a radiation treatment plan to a patient in a single radiation treatment session, the apparatus comprising:a multi-leaf collimator comprised of a plurality of pairs of selectively movable collimating leaves;a radiation-beam source; anda control circuit operably coupled to the multi-leaf collimator and the radiation-beam source and configured to administer a sequential plurality of modulated radiation doses to the patient, where the sequential plurality of modulated radiation doses includes:at least one modulated radiation dose administered by modulating the radiation beam with the multi-leaf collimator using a sliding-window pattern to provide some of, but not more than twenty-five percent of, the planned total radiation dose; anda plurality of modulated radiation doses that are each administered while modulating a radiation beam with the multi-leaf collimator using a curtain pattern wherein opposing leaves of at least some of the plurality of pairs are both moving with respect to one another and wherein at least one of the plurality of pairs of selectively movable collimating leaves moves at a different speed than another of the pairs of selectively movable collimating leaves to provide a substantial majority of, but not all of, the planned total radiation dose. 10. The apparatus of claim 9 wherein the curtain pattern comprises moving collimating leaves of the pairs of collimating leaves towards one another from an opened position. 11. The apparatus of claim 9 wherein the curtain pattern comprises moving collimating leaves of the pairs of collimating leaves away from one another from a closed position. 12. The apparatus of claim 9 wherein the control circuit is further configured to reduce a dose rate during a sub-sequence when moving collimating leaves following a completed curtain pattern to prepare to execute a follow-on curtain pattern. 13. The apparatus of claim 12 wherein reducing the dose rate does not include shutting off the radiation beam. 14. The apparatus of claim 12 wherein the control circuit is configured to administer the sequential plurality of modulated radiation doses by administering the sequential plurality of modulation doses in a particular order of treatment that minimizes a total time required for all sub-sequences to move collimating leaves following a completed curtain pattern to prepare to execute a follow-on curtain pattern. 15. The apparatus of claim 9 wherein the radiation treatment plan is formed by converting an arbitrary optimal fluence map into a plurality of curtain-pattern leaf trajectories for the multi-leaf collimator. 16. The apparatus of claim 15 wherein the radiation treatment plan is further formed by using leaf transition sub-sequences between curtain-pattern leaf trajectories.