Patent Number: 
Section: claims

1. A method comprising:receiving, in a processor, information indicative of (i) a treatment plan defining planned treatment beams, (ii) a patient volume relative to a reference, (iii) ideal intersections of the planned treatment beams with the patient volume at the time the patient is to be treated, (iv) any constraints that prevent achievement of the recommended repositioning using only the patient support, (v) an allowable change to a gantry position from a planned value and an allowable change to a collimator position from a planned value;defining, in the processor, a plurality of alternatives based at least in part on the information indicative of any constraints of the patient support and the information indicative of allowable movement of the gantry and collimator, each alternative defining a modified patient support position and modified beams, each modified beam being based at least in part on a respective one of the planned treatment beams, the change to the position of the gantry for the respective planned treatment beam and the change to the position of the collimator for the respective planned treatment beam;determining, in the processor, for each modified beam of each alternative, an intersection of the patient volume and the modified beam, with the patient volume positioned on the patient support and the patient support having the modified patient support position defined by the alternative; anddefining, in the processor, for each alternative, a measure of difference between the ideal intersections and the intersections for the modified beams of the alternative. 2. The method of claim 1 wherein the modified patient support position defined by each alternative is the same. 3. The method of claim 1 wherein the amount of change to the gantry position defined by each alternative is the same. 4. The method of claim 1 wherein the amount of change to the collimator position defined by each alternative is the same. 5. The method of claim 1 wherein for each alternative, defining the measure of difference between the ideal intersections and the intersections for the modified beams of the alternative comprises:defining, for each modified beam of the alternative, a measure of difference between the intersection and a respective one of the ideal intersections; anddefining the measure of difference between the ideal intersections and the intersections for the modified beams based at least in part on the measure of difference between the intersection and the respective one of the ideal intersections for each modified beam of the alternative. 6. The method of claim 5 wherein the measure of difference between each intersection and the respective ideal intersection is based at least in part on a distance between a point defined by the intersection and a corresponding point defined by the respective ideal intersection. 7. The method of claim 6 wherein each intersection for a modified beam defines a pyramid having a tip and a polygonal base, the tip defined by a source for the modified beam, the polygonal base having a plurality of corners, and wherein a measure of difference between each intersection and the respective ideal intersection is determined using a method comprising:defining a distance between the tip of the intersection and a tip of the respective ideal intersection;defining a square of the distance between the tips;defining for each corner of the polygonal base of the intersection, a distance between the corner and a corresponding corner of the respective ideal intersection;defining a square of the distance for each corner; anddefining the measure of difference based at least in part on a sum of the square of the distance between the tips and the square of the distance defined for each corner of the polygon. 8. The method of claim 1 wherein for each alternative, defining the measure of difference between the ideal intersections and the intersections for the modified beams of the alternative comprises:defining, for each modified beam of the alternative, a measure of difference between the intersection and a respective one of the ideal intersections;defining, for each modified beam of the alternative, a weighted difference defined as a product of a weight and the measure of difference between the intersection and a respective one of the ideal intersections, wherein the weight is based at least in part on a dosimetric strength of the modified beam relative to respective dosimetric strengths of the other modified beams of the alternative; anddefining the measure of difference between the ideal intersections and the intersections for the modified beams based at least in part on the weighted difference for each modified beam of the alternative. 9. The method of claim 8 wherein the measure of difference between the ideal intersections and the intersections for the modified beams is based at least in part on the sum of the weighted difference for each modified beam of the alternative. 10. The method of claim 1 further comprising selecting one alternative of the plurality of alternatives based at least in part on the measure of difference for the one alternative. 11. The method of claim 1 further comprising:selecting one alternative of the plurality of alternatives for which the measure of difference between the ideal intersections and the intersections for the modified beams of the alternative is no greater than the measure of difference between the ideal intersections and the intersections for the modified beams of the other alternatives. 12. Apparatus comprising:a processor to:receive information indicative of (i) a treatment plan defining planned treatment beams, (ii) a patient volume relative to a reference, (iii) ideal intersections of the planned treatment beams with the patient volume at the time the patient is to be treated, (iv) any constraints that prevent achievement of the recommended repositioning using only the patient support, (v) an allowable change to a gantry position from a planned value and an allowable change to a collimator position from a planned value;define a plurality of alternatives based at least in part on the information indicative of any constraints of the patient support and the information indicative of allowable movement of the gantry and collimator, each alternative defining a modified patient support position and modified beams, each modified beam being based at least in part on a respective one of the planned treatment beams, the change to the position of the gantry for the respective planned treatment beam and the change to the position of the collimator for the respective planned treatment beam;determine for each modified beam of each alternative, an intersection of the patient volume and the modified beam, with the patient volume positioned on the patient support and the patient support having the modified patient support position defined by the alternative; anddefine for each alternative, a measure of difference between the ideal intersections and the intersections for the modified beams of the alternative. 13. The apparatus of claim 12 wherein the modified patient support position defined by each alternative is the same. 14. The apparatus of claim 12 wherein the amount of change to the gantry position defined by each alternative is the same. 15. The apparatus of claim 12 wherein the amount of change to the collimator position defined by each alternative is the same. 16. The apparatus of claim 12 wherein the processor comprises a processor to:define, for each modified beam of the alternative, a measure of difference between the intersection and a respective one of the ideal intersections; anddefine the measure of difference between the ideal intersections and the intersections for the modified beams based at least in part on the measure of difference between the intersection and the respective one of the ideal intersections for each modified beam of the alternative. 17. The apparatus of claim 16 wherein the measure of difference between each intersection and the respective ideal intersection is based at least in part on a distance between a point defined by the intersection and a corresponding point defined by the respective ideal intersection. 18. The apparatus of claim 17 wherein each intersection for a modified beam defines a pyramid having a tip and a polygonal base, the tip defined by a source for the modified beam, the polygonal base having a plurality of corners, and wherein the processor comprises a processor to:define a distance between the tip of the intersection and a tip of the respective ideal intersection;define a square of the distance between the tips;define for each corner of the polygonal base of the intersection, a distance between the corner and a corresponding corner of the respective ideal intersection;define a square of the distance for each corner; anddefine the measure of difference based at least in part on a sum of the square of the distance between the tips and the square of the distance defined for each corner of the polygon. 19. The apparatus of claim 12 wherein the processor comprises a processor to:define, for each modified beam of the alternative, a measure of difference between the intersection and a respective one of the ideal intersections;define, for each modified beam of the alternative, a weighted difference defined as a product of a weight and the measure of difference between the intersection and a respective one of the ideal intersections, wherein the weight is based at least in part on a dosimetric strength of the modified beam relative to respective dosimetric strengths of the other modified beams of the alternative;and define the measure of difference between the ideal intersections and the intersections for the modified beams based at least in part on the weighted difference for each modified beam of the alternative. 20. The apparatus of claim 19 wherein the measure of difference between the ideal intersections and the intersections for the modified beams is based at least in part on the sum of the weighted difference for each modified beam of the alternative. 21. The apparatus of claim 12 wherein the processor comprises a processor to select one alternative of the plurality of alternatives based at least in part on the measure of difference for the one alternative. 22. The apparatus of claim 12 wherein the processor comprises a processor to select one alternative of the plurality of alternatives for which the measure of difference between the ideal intersections and the intersections for the modified beams of the alternative is no greater than the measure of difference between the ideal intersections and the intersections for the modified beams of the other alternatives. 23. An article comprising:a processor readable storage medium having stored thereon instructions that if executed by a processor, result in the following:receiving information indicative of (i) a treatment plan defining planned treatment beams, (ii) a patient volume relative to a reference, (iii) ideal intersections of the planned treatment beams with the patient volume at the time the patient is to be treated, (iv) any constraints that prevent achievement of the recommended repositioning using only the patient support, (v) an allowable change to a gantry position from a planned value and an allowable change to a collimator position from a planned value;defining a plurality of alternatives based at least in part on the information indicative of any constraints of the patient support and the information indicative of allowable movement of the gantry and collimator, each alternative defining a modified patient support position and modified beams, each modified beam being based at least in part on a respective one of the planned treatment beams, the change to the position of the gantry for the respective planned treatment beam and the change to the position of the collimator for the respective planned treatment beam;determining for each modified beam of each alternative, an intersection of the patient volume and the modified beam, with the patient volume positioned on the patient support and the patient support having the modified patient support position defined by the alternative; anddefining for each alternative, a measure of difference between the ideal intersections and the intersections for the modified beams of the alternative. 24. The article of claim 23 wherein the modified patient support position defined by each alternative is the same. 25. The article of claim 23 wherein the amount of change to the gantry position defined by each alternative is the same. 26. The article of claim 25 wherein the measure of difference between each intersection and the respective ideal intersection is based at least in part on a distance between a point defined by the intersection and a corresponding point defined by the respective ideal intersection. 27. The article of claim 26 wherein the measure of difference between the ideal intersections and the intersections for the modified beams is based at least in part on the sum of the weighted difference for each modified beam of the alternative. 28. The article of claim 23 wherein the amount of change to the collimator position defined by each alternative is the same. 29. The article of claim 28 wherein each intersection for a modified beam defines a pyramid having a tip and a polygonal base, the tip defined by a source for the modified beam, the polygonal base having a plurality of corners, and wherein a measure of difference between each intersection and the respective ideal intersection is determined using a article comprising:defining a distance between the tip of the intersection and a tip of the respective ideal intersection;defining a square of the distance between the tips;defining for each corner of the polygonal base of the intersection, a distance between the corner and a corresponding corner of the respective ideal intersection;defining a square of the distance for each corner; anddefining the measure of difference based at least in part on a sum of the square of the distance between the tips and the square of the distance defined for each corner of the polygon. 30. The article of claim 23 wherein for each alternative, defining the measure of difference between the ideal intersections and the intersections for the modified beams of the alternative comprises:defining, for each modified beam of the alternative, a measure of difference between the intersection and a respective one of the ideal intersections; anddefining the measure of difference between the ideal intersections and the intersections for the modified beams based at least in part on the measure of difference between the intersection and the respective one of the ideal intersections for each modified beam of the alternative. 31. The article of claim 23 wherein for each alternative, defining the measure of difference between the ideal intersections and the intersections for the modified beams of the alternative comprises:defining, for each modified beam of the alternative, a measure of difference between the intersection and a respective one of the ideal intersections;defining, for each modified beam of the alternative, a weighted difference defined as a product of a weight and the measure of difference between the intersection and a respective one of the ideal intersections, wherein the weight is based at least in part on a dosimetric strength of the modified beam relative to respective dosimetric strengths of the other modified beams of the alternative;and defining the measure of difference between the ideal intersections and the intersections for the modified beams based at least in part on the weighted difference for each modified beam of the alternative. 32. The article of claim 23 wherein the method further comprises selecting one alternative of the plurality of alternatives based at least in part on the measure of difference for the one alternative. 33. The article of claim 23 wherein the method further comprises selecting one alternative of the plurality of alternatives for which the measure of difference between the ideal intersections and the intersections for the modified beams of the alternative is no greater than the measure of difference between the ideal intersections and the intersections for the modified beams of the other alternatives.