Patent Number: 
Section: claims

1. An accelerator system, comprising:a ray source;a multi-leaf collimator comprising:a plurality of leaves;a multi-leaf collimator controller configured to control each of the plurality of leaves to move according to a predetermined position of each of the plurality of leaves; anda leaf position determining device which is configured to:obtain a three-dimensional image of the multi-leaf collimator;determine a sub-field shape and a sub-field size of the multi-leaf collimator according to the three-dimensional image;determine an actual position of each of the plurality of leaves according to the sub-field shape and the sub-field size; andobtain an error value for each of the plurality of leaves by comparing the actual position with the predetermined position for each of the plurality of leaves, wherein the error value for each of the plurality of leaves is used to control operation of the accelerator system. 2. The accelerator system according to claim 1, wherein the leaf position determining device is further configured to:obtain a sectional image of the multi-leaf collimator in a cross sectional direction of the multi-leaf collimator with the three-dimensional image; anddetermine the sub-field shape and the sub-field size according to the sectional image. 3. The accelerator system according to claim 1, wherein the leaf position determining device comprises a three-dimensional scanner configured to obtain the three-dimensional image of the multi-leaf collimator by performing a three-dimensional scan on the multi-leaf collimator with an emitted structured light beam. 4. The accelerator system according to claim 3, wherein the leaf position determining device further comprises a reflector configured to reflect the structured light beam to the multi-leaf collimator for performing the three-dimensional scan. 5. The accelerator system according to claim 4, wherein an area of the structured light beam passing through the multi-leaf collimator is the same as an area of a ray beam emitted from the ray source passing through the multi-leaf collimator. 6. The accelerator system according to claim 4, wherein,the reflector is located between the ray source and the multi-leaf collimator; anda reflecting layer of the reflector faces the multi-leaf collimator. 7. The accelerator system according to claim 6, wherein,a distance for the structured light beam travelling to the reflector is equal to a distance for the ray beam emitted from the ray source travelling to the reflector; andan area on which the structured light beam is irradiated to the reflector is the same as an area through which the ray beam penetrates the reflector. 8. The accelerator system according to claim 7, wherein,the three-dimensional scanner is parallel to the multi-leaf collimator; andthe reflector is at 45 degrees with respect to an axis of the structured light beam. 9. A method of controlling an accelerator system, comprising:controlling each of leaves of a multi-leaf collimator in the accelerator system to move according to a predetermined position of each of the leaves;obtaining a three-dimensional image of the multi-leaf collimator;determining a sub-field shape and a sub-field size of the multi-leaf collimator according to the three-dimensional image;determining an actual position of each of the leaves of the multi-leaf collimator according to the sub-field shape and the sub-field size;obtaining an error value for each of the leaves according to the actual position and the predetermined position for each of the leaves; andcontrolling operation of the accelerator system according to the error value for each of the leaves. 10. The method according to claim 9, wherein obtaining the three-dimensional image of the multi-leaf collimator comprises:obtaining the three-dimensional image of the multi-leaf collimator with a leaf position determining device in the accelerator system, wherein the leaf position determining device comprises a three-dimensional scanner and a reflector. 11. The method according to claim 10, wherein obtaining the three-dimensional image of the multi-leaf collimator comprises:controlling the three-dimensional scanner to emit a structured light beam,reflecting the structured light beam to the multi-leaf collimator by the reflector;collecting reflected light information from each of the leaves of the multi-leaf collimator, wherein the reflected light information comprises a three-dimensional coordinate and a reflected light intensity of each of the leaves of the multi-leaf collimator; andreconstructing the three-dimensional image of the multi-leaf collimator according to the reflected light information. 12. The method according to claim 9, wherein controlling the operation of the accelerator system according to the error value for each of the leaves comprises:continuously operating the accelerator system when the error value for each of the leaves is within a preset threshold range; andstopping the accelerator system when the error value for any one of the leaves is out of the threshold range. 13. The method according to claim 11, wherein,a distance for the structured light beam travelling to the reflector is equal to a distance for a ray beam emitted by a ray source in the accelerator system travelling to the reflector; andan area on which the structured light beam is irradiated to the reflector is the same as an area through which the ray beam penetrates the reflector. 14. The method according to claim 13, wherein,the reflector is located between the ray source and the multi-leaf collimator; anda reflecting layer of the reflector faces the multi-leaf collimator. 15. The method according to claim 11, wherein,the three-dimensional scanner is parallel to the multi-leaf collimator; andthe reflector is at 45 degrees with respect to an axis of the structured light beam. 16. The method according to claim 11, further comprising:adjusting the position of the three-dimensional scanner such that an area of the structured light beam passing through the multi-leaf collimator is the same as an area of a ray beam emitted from the ray source passing through the multi-leaf collimator. 17. The method according to claim 9, wherein determining the sub-field shape and the sub-field size of the multi-leaf collimator according to the three-dimensional image comprises:obtaining a sectional image of the multi-leaf collimator in a cross sectional direction of the multi-leaf collimator according to the three-dimensional image; anddetermining the sub-field shape and the sub-field size according to the sectional image.