Patent Number: 
Section: claims

1. A collimator comprising:a leaf movable between a first position and a second position;a leaf shaft having a proximal portion and a distal portion, and wherein the distal portion of the shaft is attached to the leaf;a spring system coupled to the leaf; andan actuator system coupled to the leaf shaft wherein a motive force generated by the spring system and a motive force generated by the actuator system longitudinally translate the leaf from the first to the second position, and wherein the actuator system is configured to selectively retain the leaf at the first position or the second position, andwherein the actuator system comprises a first electromagnet and a second electromagnet separated by a space from the first electromagnet, and a ferromagnetic movable member movable across the space between the first and second electromagnets, wherein the leaf shaft is connected to the movable member, and wherein the actuator system comprises a first configuration wherein either the first or second electromagnet is activated such that the movable member is secured at a location of either the first or second electromagnet, and a second configuration wherein the first and second electromagnets are alternately activated such that the movable member is movable within the space. 2. The collimator of claim 1, wherein the motive force generated by the actuator system is sufficient to overcome losses in the spring system. 3. The collimator of claim 1, wherein the actuator system comprises a voice coil. 4. The collimator of claim 1, wherein the spring system comprises at least one coil spring. 5. The collimator of claim 1, wherein each of the first and second electromagnets comprises a pair of adjacent coil windings each having a lumen therethrough and a C-shaped core extending through the lumens of both of the coil windings. 6. The collimator of claim 1, wherein the movable member comprises a permanent magnet. 7. The collimator of claim 1, wherein the actuator system comprises a linear actuator. 8. The collimator of claim 1, wherein when the actuator system is in the first configuration, the leaf is in a closed configuration and wherein when the actuator system is in the second configuration, the leaf is in an open configuration, and wherein the spring system and actuator system are configured to transition the leaf between the closed configuration and open configuration in about 6 ms or less. 9. The collimator of claim 1, wherein the spring system comprises at least one torsion bar spring. 10. The collimator of claim 1, wherein the spring system is coupled to the leaf shaft. 11. The collimator of claim 10, wherein the spring system and the actuator system are coupled to the proximal portion of the leaf shaft. 12. The collimator of claim 11, wherein the spring system and the actuator system are attached to the proximal portion of the leaf shaft. 13. The collimator of claim 1, wherein the motive force generated by the spring system and the motive force generated by the actuator system longitudinally translate the leaf from the second position to the first position. 14. The collimator of claim 1, wherein the actuator system comprises a piezo actuator.