High bandwidth binary multi-leaf collimator design
Described herein are multi-leaf collimators that comprise leaf drive mechanisms. The leaf drive mechanisms can be used in binary multi-leaf collimators used in emission-guided radiation therapy. One variation of a multi-leaf collimator comprises a pneumatics-based leaf drive mechanism. Another variation of a multi-leaf collimator comprises a spring-based leaf drive mechanism having a spring resonator.
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; and
an 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 position to the second position, and wherein the actuator system is configured to selectively retain the leaf at the first position or the second position, and
wherein the actuator system comprises a barrel comprising a longitudinal lumen, a first side opening, and a second side opening, and a piston located within the longitudinal lumen of the barrel, wherein the piston comprises the shaft and a piston seal coupled to the shaft within the barrel, and wherein movement of the piston within the barrel translates the leaf between the first position and the second position, and wherein the movement of the piston is controlled by fluid flow through the first and second side openings.
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 has a first configuration wherein the leaf is retained in the first position and a second configuration wherein the leaf is retained in the second position.
4. The collimator of claim 1 , wherein the spring system comprises a first spring disposed along a first length of the shaft and a second spring disposed along a second length of the shaft, the first and second springs configured such that the piston seal moves between the first side opening and the second side opening.
5. The collimator of claim 4 , wherein the first spring and the second spring are located within the barrel lumen.
6. The collimator of claim 5 , wherein the first spring is in contact with the piston on a first side and the second spring is in contact with the piston on a second side that is opposite the first side.
7. The collimator of claim 4 , wherein the first spring is located outside of the barrel lumen between a spring retainer and a first end wall of the barrel.
8. The collimator of claim 1 , further comprising a fluid source connected to the first side opening and the second side opening.
9. The collimator of claim 8 , further comprising a first valve between the first side opening and the fluid source and a second valve between the second side opening and the fluid source, wherein the first and second valves selectively regulate fluid flow into and out of the barrel lumen.
10. The collimator of claim 8 , wherein the fluid source comprises a pressurized air source.
11. The collimator of claim 8 , wherein injecting fluid from the fluid source into the first side opening and not the second side opening causes the piston to move the leaf to the first position.
12. The collimator of claim 8 , wherein injecting fluid from the fluid source into the second side opening and not the first side opening causes the piston to move the leaf to the second position.
13. The collimator of claim 12 , wherein injecting fluid into the second side opening comprises creating sufficient pressure to hold the leaf in the second position.
14. The collimator of claim 1 , wherein the spring system comprises at least one coil spring.
15. The collimator of claim 5 , wherein the piston is configured to contact the first spring and not the second spring when the leaf is in the first position and to contact the second spring and not the first spring when the leaf is in the second position.
16. The collimator of claim 9 , further comprising a controller in communication with the fluid source, the first valve and the second valve, wherein the controller is configured to open and close the first valve and the second valve to selectively regulate fluid flow into and out of the barrel lumen.
17. The collimator of claim 16 , wherein the controller is configured to move the leaf to the first position by opening the first valve to the fluid source.
18. The collimator of claim 17 , wherein the controller is configured to open the second valve to atmospheric pressure prior to opening the first valve to the fluid source.
19. The collimator of claim 16 , wherein the controller is configured to move the leaf to the second position by opening the second valve to the fluid source.
20. The collimator of claim 19 , wherein the controller is configured to open the first valve to atmospheric pressure prior to opening the second valve to the fluid source.
21. The collimator of claim 1 , wherein the spring system comprises at least one torsion bar spring.
22. The collimator of claim 11 , wherein injecting fluid into the first side opening comprises creating sufficient pressure to hold the leaf in the first position.
23. The collimator of claim 17 , wherein the controller is configured to open the second valve to the fluid source when the leaf is at or near the first position to reduce piston speed.
24. The collimator of claim 19 , wherein the controller is configured to open the first valve to the fluid source when the leaf is at or near the second position to reduce piston speed.
25. The collimator of claim 1 , wherein the spring system is coupled to the leaf shaft.
26. The collimator of claim 25 , wherein the spring system and the actuator system are coupled to the proximal portion of the leaf shaft.
27. The collimator of claim 26 , wherein the spring system and the actuator system are attached to the proximal portion of the shaft.
28. 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.
29. The collimator of claim 1 , wherein the spring system and the actuator system are configured to translate the leaf from the first position to the second position in about 10 ms or less.
30. The collimator of claim 29 , wherein the spring system and the actuator system are configured to translate the leaf from the first position to the second position in about 6 ms or less.