Method and a system for optimizing a radiation treatment plan based on a reference dose distribution

1. A computer-based method for generating an improved radiation therapy treatment plan used for a radiation therapy apparatus for a treatment volume of a body having a target and an organ-at-risk, the method comprising:

accessing an existing radiation therapy treatment plan for the treatment volume from a memory of a computer, a dose distribution of the existing radiation therapy treatment plan serving as a reference dose distribution, the existing radiation therapy treatment plan being previously created for radiation treatment with the radiation therapy apparatus for the treatment volume of the body of a patient having the target area and the organ-at-risk; and

performing machine parameter optimization for machine parameters of a radiation therapy apparatus on the existing radiation therapy treatment plan for the treatment volume with the computer and using the dose distribution of the existing radiation therapy treatment plan as the reference dose distribution, by pursuing an optimization goal to minimize doses to volume units of the organ-at-risk by simulating variation of the machine parameters of the radiation therapy apparatus and calculating a direct relationship between the variation of the machine parameters and a variation of the doses to the volume units, thereby generating the improved radiation therapy treatment plan, wherein at least one optimization function relates the reference dose distribution to a dose distribution of the improved radiation therapy treatment plan throughout the machine parameter optimization, wherein the radiation therapy apparatus delivers radiation according to the improved radiation therapy treatment plan.

2. The computer-based method according to claim 1 , wherein said pursuing the optimization goal includes:

minimizing a sum of dose-based functions that evaluate the doses to the volume units as a direct function of the machine parameters that are administered to the organ-at-risk.

3. The computer-based method according to claim 1 , wherein said pursuing the optimization goal includes at least one of:

aiming that voxels of the organ-at-risk do not receive a dose that is higher than the reference dose distribution for the organ-at-risk of the existing radiation therapy treatment plan;

aiming that voxels of the target do not receive a dose that is lower than a reference dose of each corresponding voxel of the existing radiation therapy treatment plan, or do not receive a dose that is lower than the prescribed dose to the target; and

aiming that voxels of the target do not receive a dose that is higher than a reference dose of each corresponding voxel of the existing radiation therapy treatment plan, or do not receive a dose that is higher than the prescribed dose to the target.

4. The computer-based method according to claim 1 , wherein said pursuing the optimization goal includes at least one of:

aiming that a dose-volume-histogram dose of the organ-at-risk is not higher than a corresponding dose of a reference dose-volume-histogram for the organ-at-risk of the existing radiation therapy treatment plan;

aiming that a dose-volume-histogram dose of the target is not lower than a corresponding dose of a reference dose-volume-histogram of the existing radiation therapy treatment plan, or is not lower than the prescribed dose to the target; and

aiming that a dose-volume-histogram dose of the target is not higher than a corresponding dose of a reference dose-volume-histogram of the existing radiation therapy treatment plan, or is not higher than the prescribed dose to the target.

5. The computer-based method according to claim 1 , further comprising:

displaying a dose-volume histogram for a portion of the organ-at-risk for the existing radiation therapy treatment plan; and

displaying a dose-volume histogram for said portion of the organ-at-risk for the improved radiation therapy treatment plan.

6. The computer-based method according to claim 1 , wherein said step of performing machine parameter optimization further comprises:

replacing a positive part function used to pursue the optimization goal with a log-sum-exp function having non-zero gradients.

7. The computer-based method according to claim 1 , wherein the step of performing machine parameter optimization further comprises:

generating the improved radiation therapy treatment plan that reduces the integral dose of the existing radiation therapy treatment plan.

8. A computer system for generating an improved radiation therapy treatment plan used for a radiation therapy apparatus for a treatment volume of a body having a target and an organ-at-risk, the system comprising:

a storage device for storing an existing radiation therapy treatment plan for the treatment volume, a dose distribution of the existing radiation therapy treatment plan serving as a reference dose distribution, the existing radiation therapy treatment plan being previously created for radiation treatment with the radiation therapy apparatus for the treatment volume of the body of a patient having the target area and the organ-at-risk; and

a hardware processor for performing machine parameter optimization for parameters of the radiation therapy apparatus on the existing radiation therapy treatment plan for the treatment volume and using the dose distribution of the existing radiation therapy treatment plan as the reference dose distribution by pursuing an optimization goal to minimize doses to volume units of the organ-at-risk by simulating a variation of the machine parameters of the radiation therapy apparatus and calculating a direct relationship between the variation of the machine parameters and a variation of the doses to the volume units, thereby generating the improved radiation therapy treatment plan,

wherein at least one optimization function relates the reference dose distribution to a dose distribution of the improved radiation therapy treatment plan throughout the machine parameter optimization, wherein the radiation therapy apparatus delivers radiation according to the improved radiation therapy treatment plan.

9. The computer system according to claim 8 , wherein said pursuing the optimization goal includes:

minimizing a sum of dose-based functions that evaluate the doses to the volume units as a direct function of the machine parameters that are administered to the organ-at-risk.

10. The computer system according to claim 8 , wherein said pursuing the optimization goal includes at least one of:

aiming that voxels of the organ-at-risk do not receive a dose that is higher than the reference dose distribution for the organ-at-risk of the existing radiation therapy treatment plan;

aiming that voxels of the target do not receive a dose that is lower than a reference dose of each corresponding voxel of the existing radiation therapy treatment plan, or do not receive a dose that is lower than the prescribed dose to the target; and

aiming that voxels of the target do not receive a dose that is higher than a reference dose of each corresponding voxel of the existing radiation therapy treatment plan, or do not receive a dose that is higher than the prescribed dose to the target.

11. The computer system according to claim 8 , wherein said pursuing the optimization goal includes at least one of:

aiming that a dose-volume-histogram dose of the organ-at-risk is not higher than a corresponding dose of a reference dose-volume-histogram for the organ-at-risk of the existing radiation therapy treatment plan;

aiming that a dose-volume-histogram dose of the target is not lower than a corresponding dose of a reference dose-volume-histogram of the existing radiation therapy treatment plan, or is not lower than the prescribed dose to the target; and

aiming that a dose-volume-histogram dose of the target is not higher than a corresponding dose of a reference dose-volume-histogram of the existing radiation therapy treatment plan, or is not higher than the prescribed dose to the target.

12. The computer system according to claim 8 , further comprising:

a display device for displaying a dose-volume histogram for a portion of the organ-at-risk for the existing radiation therapy treatment plan, and for displaying a dose-volume histogram for said portion of the organ-at-risk for the improved radiation therapy treatment plan.

13. The computer system according to claim 8 , wherein the hardware processor that performs machine parameter optimization further replaces a positive part function used to pursue the optimization goal with a log-sum-exp function having non-zero gradients.

14. The computer system according to claim 8 , wherein the hardware processor that performs machine parameter optimization further generates the improved radiation therapy treatment plan by reducing the integral dose of the existing radiation therapy treatment plan.

15. A non-transitory computer readable medium having computer instructions recorded thereon, the computer instructions configured to perform a method for generating an improved radiation therapy treatment plan used for a radiation therapy apparatus for a treatment volume having a target and an organ-at-risk when executed on a computer, the method comprising the steps of:

accessing an existing radiation therapy treatment plan for the treatment volume from a memory of a computer, a dose distribution of the existing radiation therapy treatment plan serving as a reference dose distribution, the existing radiation therapy treatment plan being previously created for radiation treatment with the radiation therapy apparatus for the treatment volume of the body of a patient having the target area and the organ-at-risk; and

performing machine parameter optimization for machine parameters of the radiation therapy apparatus on the existing radiation therapy treatment plan with the computer and using the dose distribution of the existing radiation therapy treatment plan for the treatment volume as the reference dose distribution, by pursuing an optimization goal to minimize doses to volume units the organ-at-risk by simulating a variation of the machine parameters of the radiation therapy apparatus and calculating a direct relationship between the variation of the machine parameters and a variation of the doses to the volume units, thereby generating the improved radiation therapy treatment plan,

wherein at least one optimization function relates the reference dose distribution to a dose distribution of the improved radiation therapy treatment plan throughout the machine parameter optimization, wherein the radiation therapy apparatus delivers radiation according to the improved radiation therapy treatment plan.

16. The non-transitory computer readable medium according to claim 15 , wherein said pursuing the optimization goal includes:

minimizing a sum of dose-based functions that evaluate the doses to the volume units as a direct function of the machine parameters that are administered to the organ-at-risk.

17. The non-transitory computer readable medium according to claim 15 , wherein said pursuing the optimization goal includes at least one of:

aiming that voxels of the organ-at-risk do not receive a dose that is higher than the reference dose distribution for the organ-at-risk of the existing radiation therapy treatment plan;

aiming that voxels of the target do not receive a dose that is lower than a reference dose of each corresponding voxel of the existing radiation therapy treatment plan, or do not receive a dose that is lower than the prescribed dose to the target; and

aiming that voxels of the target do not receive a dose that is higher than a reference dose of each corresponding voxel of the existing radiation therapy treatment plan, or do not receive a dose that is higher than the prescribed dose to the target.

18. The non-transitory computer readable medium according to claim 15 , wherein said pursuing the optimization goal includes at least one of:

aiming that a dose-volume-histogram dose of the organ-at-risk is not higher than a corresponding dose of a reference dose-volume-histogram for the organ-at-risk of the existing radiation therapy treatment plan;

aiming that a dose-volume-histogram dose of the target is not lower than a corresponding dose of a reference dose-volume-histogram of the existing radiation therapy treatment plan, or is not lower than the prescribed dose to the target; and

aiming that a dose-volume-histogram dose of the target is not higher than a corresponding dose of a reference dose-volume-histogram of the existing radiation therapy treatment plan, or is not higher than the prescribed dose to the target.

19. The non-transitory computer readable medium according to claim 15 , said method further comprising:

displaying a dose-volume histogram for a portion of the organ-at-risk for the existing radiation therapy treatment plan; and

displaying a dose-volume histogram for said portion of the organ-at-risk for the improved radiation therapy treatment plan.

20. The non-transitory computer readable medium according to claim 15 , wherein said step of performing machine parameter optimization further comprises:

replacing a positive part function used to pursue the optimization goal with a log-sum-exp function having non-zero gradients.

21. The non-transitory computer readable medium according to claim 15 , wherein the step of performing machine parameter optimization further comprises:

generating the improved radiation therapy treatment plan that reduces the integral dose of the existing radiation therapy treatment plan.

22. The computer-based method according to claim 1 , wherein the machine parameters include at least one of bixel weights, spot weights, multi-leaf collimator leaf positions, jaw positions, segment weights, monitor units, collimator angles, couch angles, gantry angles, wedge angles, and arc delivery times.

23. The computer system according to claim 8 , wherein the machine parameters include at least one of bixel weights, spot weights, multi-leaf collimator leaf positions, jaw positions, segment weights, monitor units, collimator angles, couch angles, gantry angles, wedge angles, and arc delivery times.

24. The non-transitory computer readable medium according to claim 15 , wherein the machine parameters include at least one of bixel weights, spot weights, multi-leaf collimator leaf positions, jaw positions, segment weights, monitor units, collimator angles, couch angles, gantry angles, wedge angles, and arc delivery times.

25. The computer-based method according to claim 1 , wherein said pursuing the optimization goal includes:

minimizing a sum of dose-based functions that evaluate the doses to the volume units with a non-linear direct relationship to the machine parameters that are administered to the organ-at-risk.

26. The computer system according to claim 8 , wherein said pursuing the optimization goal includes:

minimizing a sum of dose-based functions that evaluate the doses to the volume units with a non-linear direct relationship to the machine parameters that are administered to the organ-at-risk.

27. The non-transitory computer readable medium according to claim 15 , wherein said pursuing the optimization goal includes:

minimizing a sum of dose-based functions that evaluate the doses to the volume units with a non-linear direct relationship to the machine parameters that are administered to the organ-at-risk.