Mixed-energy intensity-modulated radiation therapy

1. A method comprising:

determining, by a processor, a plurality of radiation beams for a radiation treatment fraction, each of the plurality of beams associated with a respective intensity, beam aperture and beam energy, and at least two of the plurality of beams respectively associated with two different beam energies;

determining, by the processor, a forward dose associated with the plurality of beams;

determining, by the processor, that the forward dose does not conform to a dose prescription;

determining, using Gaussian elimination, a beam weight for each of the plurality of beams based on the forward dose and the dose prescription;

determining, by the processor, that the beam weight for at least one of the plurality of beams is negative;

changing the at least one beam aperture associated with the at least one of the plurality of beams;

determining, by the processor, a second beam weight for each of the plurality of beams based on the changed at least one beam aperture; and

determining, by the processor, a second forward dose associated with the plurality of beams and the second beam weights.

2. A method according to claim 1 , further comprising:

delivering the plurality of beams to a patient volume in a single treatment fraction according to their respective intensity, beam aperture and beam energy.

3. A method according to claim 2 , wherein delivering the plurality of beams comprises:

delivering one of the at least two of the plurality of beams at a first beam energy from a therapeutic radiation source;

changing a configuration of the therapeutic radiation source to generate beams at a second beam energy; and

delivering a second one of the at least two of the plurality of beams at the second beam energy from the therapeutic radiation source.

4. A method according to claim 3 , wherein the one of the at least two of the plurality of beams is delivered while the patient volume is in a first position, and

wherein the second one of the at least two of the plurality of beams is delivered while the patient volume is in the first position.

5. A method according to claim 1 , wherein the two different beam energies are megavoltage energies.

6. A non-transitory medium having processor-executable program code stored thereon, the medium comprising:

code to determine a plurality of radiation beams for a radiation treatment fraction, each of the plurality of beams associated with a respective intensity, beam aperture and beam energy, and at least two of the plurality of beams respectively associated with two different beam energies;

code to determine a forward dose associated with the plurality of beams;

code to determine that the forward dose does not conform to a dose prescription; determine, using Gaussian elimination, a beam weight for each of the plurality of beams based on the forward dose and the dose prescription;

code to determine that the beam weight for at least one of the plurality of beams is negative;

code to change the at least one beam aperture associated with the at least one of the plurality of beams;

code to determine a second beam weight for each of the plurality of beams based on the changed at least one beam aperture; and

code to determine a second forward dose associated with the plurality of beams and the second beam weights.

7. A medium according to claim 6 , further comprising:

code to deliver the plurality of beams to a patient volume in a single treatment fraction according to their respective intensity, beam aperture and beam energy.

8. A medium according to claim 7 , wherein delivering the plurality of beams comprises:

delivering one of the at least two of the plurality of beams at a first beam energy from a therapeutic radiation source;

changing a configuration of the therapeutic radiation source to generate beams at a second beam energy; and

delivering a second one of the at least two of the plurality of beams at the second beam energy from the therapeutic radiation source.

9. A medium according to according to claim 8 , wherein the one of the at least two of the plurality of beams is delivered while the patient volume is in a first position, and wherein the second one of the at least two of the plurality of beams is delivered while the patient volume is in the first position.

10. A medium according to claim 6 , wherein the two different beam energies are megavoltage energies.