Patent Number: 
Section: claims

1. A method for calibrating an X-ray apparatus, which includes an X-ray detector and a collimator, comprising:moving the X-ray detector from a first position to a second position along a first axis of a coordinate system, wherein the first position is under a scanning table, and the second position is outside the scanning table;moving the collimator to align the collimator with the X-ray detector at the second position;determining one or more parameters, wherein the one or more parameters include at least one of a distance between the first position and the second position, or a first value of a first encoder of the collimator when the collimator is aligned with the X-ray detector at the second position, wherein the first encoder detects a movement of the collimator along the first axis of the coordinate system; anddetermining a second value of the first encoder when the collimator is aligned with the X-ray detector at the first position based on the distance between the first position and the second position and the first value of the first encoder. 2. The method of claim 1, wherein the moving the collimator to align the collimator with the X-ray detector comprises:moving the collimator to align a center of a beam field of the collimator with a center of an imaging region of the X-ray detector at the second position. 3. The method of claim 1, wherein the first position has a first reference coordinate along the first axis and/or a second reference coordinate along a second axis of the coordinate system. 4. The method of claim 1, further comprising:moving the X-ray detector back to the first position; andmoving the collimator based on the second value of the first encoder so that the collimator is aligned with the X-ray detector at the first position. 5. The method of claim 4, wherein the collimator further includes a second encoder and a third encoder, wherein the second encoder detects a movement of the collimator along a second axis of the coordinate system, and the third encoder detects a movement of the collimator along a third axis of the coordinate system. 6. The method of claim 5, wherein the one or more parameters further includes a value of the second encoder and a value of the third encoder when the collimator is aligned with the X-ray detector at the second position, and the moving the collimator so that the collimator is aligned with the X-ray detector at the first position further comprises:moving the collimator based on the second value of the first encoder, the value of the second encoder, and the value of the third encoder. 7. The method of claim 1, wherein the X-ray detector includes a fourth encoder and a fifth encoder, wherein the fourth encoder detects a movement of the X-ray detector along a second axis of the coordinate system, the fifth encoder detects a movement of the X-ray detector along a third axis of the coordinate system. 8. The method of claim 7, wherein the one or more parameters further includes a value of the fourth encoder and a value of the fifth encoder when the X-ray detector is at the second position, wherein the value of the fourth encoder corresponds to a second reference coordinate of the X-ray detector along the second axis, and the value of the fifth encoder corresponds to a third reference coordinate of the X-ray detector along the third axis. 9. The method of claim 7, wherein the X-ray detector further includes a sixth encoder, wherein the sixth encoder detects a movement of the X-ray detector along the first axis of the coordinate system and detects a coordinate of the second position of the X-ray detector along the first axis. 10. The method of claim 1, wherein the determining a second value of the first encoder comprises:determining the second value of the first encoder based on the first value of the first encoder, a coefficient of the first encoder, and the distance between the first position and the second position. 11. The method of claim 1, wherein the collimator and the X-ray detector are aligned periodically. 12. A system for calibrating an X-ray apparatus, which includes an X-ray detector and a collimator, comprising:at least one storage device including a set of instructions;at least one processor in communication with the at least one storage device, wherein when executing the set of instructions, the at least one processor is configured to cause the system to:move the X-ray detector from a first position to a second position along a first axis of a coordinate system, wherein the first position is under a scanning table, and the second position is outside the scanning table;move the collimator to align the collimator with the X-ray detector at the second position;determine one or more parameters, wherein the one or more parameters include at least one of a distance between the first position and the second position, or a first value of a first encoder of the collimator when the collimator is aligned with the X-ray detector at the second position, wherein the first encoder detects a movement of the collimator along the first axis of the coordinate system; anddetermine a second value of the first encoder when the collimator is aligned with the X-ray detector at the first position based on the distance between the first position and the second position and the first value of the first encoder. 13. The system of claim 12, wherein to move the collimator to align the collimator with the X-ray detector, the at least one processor is further configured to cause the system to:move the collimator to align a center of a beam field of the collimator with a center of an imaging region of the X-ray detector at the second position. 14. The system of claim 12, wherein the first position has a first reference coordinate along the first axis and/or a second reference coordinate along a second axis. 15. The system of claim 12, the at least one processor is further configured to cause the system to:move the X-ray detector back to the first position; andmove the collimator based on the second value of the first encoder so that the collimator is aligned with the X-ray detector at the first position. 16. The system of claim 15, wherein the collimator further includes a second encoder and a third encoder, wherein the second encoder detects a movement of the collimator along a second axis of the coordinate system, and the third encoder detects a movement of the collimator along a third axis of the coordinate system. 17. The system of claim 16, wherein the one or more parameters further includes a value of the second encoder and a value of the third encoder when the collimator is aligned with the X-ray detector at the second position, and to move the collimator so that the collimator is aligned with the X-ray detector at the first position, the at least one processor is further configured to cause the system to:move the collimator based on the second value of the first encoder, the value of the second encoder, and the value of the third encoder. 18. The system of claim 12, wherein the X-ray detector includes a fourth encoder and a fifth encoder, wherein the fourth encoder detects a movement of the X-ray detector along a second axis of the coordinate system, the fifth encoder detects a movement of the X-ray detector along a third axis of the coordinate system. 19. The system of claim 12, wherein to determine a second value of the first encoder, the at least one processor is configured to cause the system to:determine the second value of the first encoder based on the first value of the first encoder, a coefficient of the first encoder, and the distance between the first position and the second position. 20. A non-transitory computer-readable medium, comprising at least one set of instructions, wherein when executed by at least one processor of a computing device, the at least one set of instructions cause the at least one processor to effectuate a method comprising:moving the X-ray detector from a first position to a second position along a first axis of a coordinate system, wherein the first position is under a scanning table, and the second position is outside the scanning table;moving the collimator to align the collimator with the X-ray detector at the second position;determining one or more parameters, wherein the one or more parameters include at least one of a distance between the first position and the second position, or a first value of a first encoder of the collimator when the collimator is aligned with the X-ray detector at the second position, wherein the first encoder detects a movement of the collimator along the first axis of the coordinate system; anddetermining a second value of the first encoder when the collimator is aligned with the X-ray detector at the first position based on the distance between the first position and the second position and the first value of the first encoder.