Imaging based calibration systems, devices, and methods

1. A method for automatically positioning a target at an isocenter for each gantry angle, comprising:

generating images of the target at a plurality of gantry angles;

determining a target location for each gantry angle from the generated images;

for each gantry angle, determining a target location offset by comparing a generated image for a gantry angle with a corresponding reference image; and

correcting the target location offset for each gantry angle by:

moving the target to the isocenter; and

repositioning the target location by moving the target by a distance which equals a previously determined couch rotation dependent offset value.

2. The method of claim 1 , further comprising generating load-dependent couch offset information by measuring errors included in the motion of a couch configured to hold the target due to different loads positioned thereon.

3. The method of claim 2 , further comprising correcting the target location by combining the previously determined couch rotation dependent offset value with the load-dependent couch offset information.

4. The method of claim 3 , further comprising determining offsets for collimator jaw or MLC imperfections, wherein the correcting of the target location includes correcting the target location by combining the previously determined couch rotation dependent offset value, the load-dependent couch offset information, and the offsets for collimator jaw or MLC imperfections.

5. A method for correcting a location of a target prior to irradiating the target with a radiation beam, comprising:

positioning a target holding device at a first location relative to a gantry;

moving the gantry to a first gantry angle;

moving the target holding device to a second location, the second location corresponding to a location corrected for isocenter movement associated with the moving of the gantry to the first gantry angle; and

correcting the second location for isocenter movement associated with the moving of the target holding device to the second location.

6. The method of claim 5 , further comprising automatically correcting the location of the target.

7. The method of claim 5 , further comprising automatically correcting the location of the target for a plurality of gantry angles.

8. The method of claim 7 , further comprising moving the gantry to a plurality of gantry angles and storing isocenter movement values associated with the moving of the gantry to the plurality of gantry angles in a tabular format for later use.

9. The method of claim 8 , further comprising moving the target holding device to a plurality of locations associated with the plurality of gantry angles, and storing isocenter movement values associated with the moving of the target holding device to the plurality of locations in a tabular format for later use.

10. The method of claim 9 , wherein the automatically correcting the location of the target for a plurality of gantry angles and moving of the target holding device to the plurality of locations associated with the plurality of gantry angles comprises automatically correcting the location of the target for a plurality of gantry angles and associated target holding device movements based on the previously stored isocenter movement values.

11. A method for irradiating a patient positioned on a treatment couch with a radiation treatment beam from a treatment device including a gantry, comprising:

positioning the treatment couch at a first location;

moving the gantry to a first gantry angle;

moving the treatment couch to a second location, the second location corresponding to a location corrected for isocenter movement associated with the moving of the gantry to the first gantry angle;

moving the treatment couch to a third location, the third location corresponding to a location corrected for isocenter movement associated with the moving of the treatment couch to the second location; and

irradiating the patient.

12. The method of claim 11 , further comprising automatically correcting patient location for a plurality of gantry angles and associated treatment couch movements.

13. The method of claim 12 , further comprising moving the gantry to a plurality of gantry angles, and prerecording isocenter movement values associated with the moving of the gantry to the plurality of gantry angles.

14. The method of claim 13 , further comprising moving the treatment couch to a plurality of locations associated with the plurality of gantry angles, and prerecording isocenter movement values associated with the moving of the treatment couch to the plurality of locations.

15. The method of claim 14 , further comprising automatically correcting patient location for the plurality of gantry angles based on the prerecorded isocenter movement values.

16. A method for automatically positioning a target at an isocenter for a plurality of gantry angles, comprising:

generating images of the target at a plurality of gantry angles;

determining target locations for corresponding gantry angles from the generated images;

for each gantry angle in the plurality of gantry angles:

determining an isocenter offset value by comparing a generated image for a gantry angle with a corresponding reference image;

determining isocenter location based on the determined isocenter offset value; and

repositioning the target from the determined isocenter location by moving a couch holding the target by a distance which equals a previously determined couch movement related offset value.

17. The method of claim 16 , further comprising determining, for each gantry angle, a value by which the isocenter location shifted when the target is repositioned.

18. The method of claim 17 , further comprising positioning different targets on the couch, moving the couch to different locations for each target, measuring errors introduced into movement of the couch by different weights of the different targets, and generating a target-dependent offset value based on the measured errors.

19. The method of claim 18 , further comprising correcting a location of a target by combining the previously determined couch movement related offset value with the target-dependent offset value.

20. The method of claim 19 , further comprising determining offset values for collimator jaw or MLC imperfections, wherein the correcting of the location of the target includes correcting the location of the target by combining the previously determined couch movement related offset value, the target-dependent offset value, and the offset values for collimator jaw or MLC imperfections.