X-ray imaging system with a combined filter and collimator positioning mechanism
A radiation therapy system includes an X-ray imaging system that is configured with a combined and simplified filter and collimator positioning mechanism. In addition, an X-ray imager of the RT system is only positioned at a few discrete locations within a plane that is a fixed distance from the imaging X-ray source when generating X-ray images. As a result, for each of these discrete imaging positions, the simplified filter and collimator positioning mechanism positions a specific collimator-filter combination in a specific location between the X-ray source and the imager.
1. An imaging system configured to rotate about a center point of rotation, the imaging system comprising:
an X-ray source configured to direct X-rays along an X-ray path that passes through the center point of rotation to an X-ray imager;
the X-ray imager, which is positioned at a fixed imaging distance along the X-ray path from the X-ray source and is configured to generate an X-ray image from the X-rays;
a first combined filter-collimator assembly that includes a first compensation filter and a first collimator configured with a first opening;
a second combined filter-collimator assembly that includes a second compensation filter and a second collimator configured with a second opening; and
a positioning mechanism that is configured to position the second combined filter-collimator assembly out of the X-ray path and the first combined filter-collimator assembly in the X-ray path so that:
the first collimator is in the X-ray path at a first fixed distance along the X-ray path from the X-ray source and the first opening defines a width of a first imaging field; and
the first compensating filter is in the first imaging field at a second fixed distance along the X-ray path from the first collimator.
2. The imaging system of claim 1 , wherein the positioning mechanism is further configured to:
position the first combined filter-collimator assembly out of the X-ray path; and
position the second combined filter-collimator assembly in the X-ray path.
3. The imaging system of claim 2 , wherein the positioning mechanism is further configured to simultaneously position the first combined filter-collimator assembly out of the X-ray path and position the second combined filter-collimator assembly in the X-ray path.
4. The imaging system of claim 2 , wherein, when the second combined filter-collimator assembly is positioned in the X-ray path, the second collimator is disposed along the X-ray path at a third fixed distance from the X-ray source so that the second opening defines a width of a second imaging field.
5. The imaging system of claim 2 , wherein, when the second combined filter-collimator assembly is positioned in the X-ray path, the second compensating filter is in a second imaging field at a third fixed distance along the X-ray path from the second collimator.
6. The imaging system of claim 5 , wherein the third fixed distance along the X-ray path from the second collimator is different than the second fixed distance along the X-ray path from the first collimator.
7. The imaging system of claim 5 , wherein the positioning mechanism is configured to position the first collimator and the first compensating filter out of the X-ray path and position the second collimator and the second compensating filter in the X-ray path with a single mechanical operation.
8. The imaging system of claim 5 , wherein the single mechanical operation includes a motion of the first collimator, the first compensating filter, the second collimator, and the second compensating filter in a direction perpendicular to the X-ray path.
9. The imaging system of claim 1 , wherein the first collimator and the first compensating filter are fixed in position relative to each other.
10. The imaging system of claim 1 , wherein the second collimator and the second compensating filter are fixed in position relative to each other.
11. The imaging system of claim 1 , wherein the positioning mechanism is further configured to simultaneously position the second combined filter-collimator assembly out of the X-ray path and position the first combined filter-collimator assembly in the X-ray path.
12. The imaging system of claim 1 , wherein the X-ray imager is configured to:
generate images in a first imaging position, in which a first portion of the X-ray imager is disposed at the fixed imaging distance along the X-ray path from the X-ray source; and
generate images in a second imaging position, in which a second portion of the X-ray imager is disposed at the fixed imaging distance along the X-ray path from the X-ray source and the X-ray imager is displaced from the first imaging position in a direction perpendicular to the X-ray path.
13. The imaging system of claim 12 , wherein the first portion of the X-ray imager comprises a center point of an X-ray detection surface of the X-ray imager and the second portion comprises an edge portion of the X-ray imager.
14. A method of generating an X-ray image in a system that includes an X-ray source and an X-ray imager, wherein the X-ray source is configured to direct X-rays along an X-ray path that passes through a center point of rotation of the system to the X-ray imager and the X-ray imager is configured to generate an X-ray image from the X-rays, the method comprising:
positioning a first combined filter-collimator assembly in the X-ray path and a second combined filter-collimator assembly out of the X-ray path, wherein the first combined filter-collimator assembly includes a first compensating filter and a first collimator configured with a first opening and the second combined filter-collimator assembly includes a second compensating filter and a second collimator configured with a second opening;
while the imager is positioned at a fixed imaging distance along the X-ray path from the X-ray source and the first combined filter-collimator assembly is positioned in the X-ray path, rotating the X-ray source and the X-ray imager about the center point of rotation; and
while rotating the X-ray source and the X-ray imager about the center point of rotation, receiving the X-rays with the X-ray imager.
15. The method of claim 14 , wherein, while rotating the X-ray source and the X-ray imager about the center point of rotation with the first combined filter-collimator assembly positioned in the X-ray path, the first collimator is positioned in the X-ray path at a first fixed distance along the X-ray path from the X-ray source and the first compensating filter is positioned in the X-ray path at a second fixed distance along the X-ray path from the first collimator.
16. The method of claim 14 , wherein, when the first collimator is at the first fixed distance along the X-ray path from the X-ray source, the collimator defines a width of a first imaging field, wherein the first imaging field is different from a second imaging field that is defined by a second collimator of the second combined filter-collimator assembly when the second combined filter-collimator assembly is positioned in the X-ray path.
17. The method of claim 14 , wherein the first collimator and the first compensating filter are fixed in position relative to each other in the first combined filter-collimator assembly.
18. The method of claim 17 , wherein the second collimator and the second compensating filter are fixed in position relative to each other in the second combined filter-collimator assembly.
19. The method of claim 14 , wherein positioning the first combined filter-collimator assembly in the X-ray path and positioning the second combined filter-collimator assembly out of the X-ray path is performed via a single mechanical operation.
20. The method of claim 19 , wherein the single mechanical operation includes a motion of the first combined filter-collimator assembly and the second combined filter-collimator assembly in a direction perpendicular to the X-ray path.