Method for selecting beam orientations in intensity modulated radiation therapy

• US 6,504,899 B2
• Filed: 09/25/2001
• Issued: 01/07/2003
• Est. Priority Date: 09/25/2000
• Status: Expired due to Fees

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Inventors: Pugachev, Andrei, Xing, Lei
• Primary Examiner(s): BRUCE, DAVID VERNON
• Application Number:
  US09/965,585
• Publication Number:
  US 20020051513A1
• Time in Patent Office: 469 Days
• Field of Search: 378/4, 378/64, 378/65, 378/901
• US Class Current: 378/65
• CPC Class Codes: A61N 5/103 Treatment planning systems
• CPC Class Codes: A61N 5/1042 with spatial modulation of the radiation beam within the treatment head
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

A method for selecting an orientation of a treatment beam for intensity modulated radiation therapy based on analysis performed on a model of a patient geometry prior to the actual treatment includes a planning target volume (PTV) and the structures at risk. The method calls for assigning a tolerance parameter to the structures at risk, subdividing the treatment beam into beamlets, selecting a treatment parameter and selecting a set of orientations for the treatment beam and deriving a score for each of the orientations by weighting each of the beamlets so as to maximize the treatment parameter in the PTV while not exceeding the tolerance parameter in the structures at risk at each orientation. The derived scores are used to construct a scoring function to aid in the selection of one or more treatment beam orientations to be used during the actual intensity modulated radiation therapy.

Claims

1. A method for selecting an orientation of a treatment beam in intensity modulated radiation therapy, said method comprising:

a) obtaining a model of a patient geometry comprising a planning target volume and at least one structure at risk;

b) assigning a tolerance parameter to said at least one structure at risk;

c) subdividing said treatment beam into beamlets;

d) selecting a treatment parameter;

e) selecting a set of angles for said treatment beam;

f) deriving a score for each angle of said set of angles by weighting each of said beamlets to maximize said treatment parameter in said planning target volume while not exceeding said tolerance parameter in said at least one structure at risk;

g) constructing a scoring function comprising said score as a function of angle;

h) selecting at least one treatment angle based on said scoring function.

2. The method of claim 1, wherein said treatment parameter is a radiation dose.

3. The method of claim 2, wherein said tolerance parameter is a tolerance dose.

4. The method of claim 3, wherein said at least one structure at risk is a structure selected from the group consisting of internal organs, bones and tissue.

5. The method of claim 3, wherein said planning target volume comprises a tumor.

6. The method of claim 1, wherein said treatment parameter is an energy.

7. The method of claim 1, further comprising adjusting a beamlet cross section for each of said beamlets to maximize said treatment parameter in said planning target volume while not exceeding said tolerance parameter in said at least one structure at risk.

8. The method of claim 7, wherein said treatment parameter is a radiation dose.

9. The method of claim 1, wherein said at least one structure at risk is a structure selected from the group consisting of internal organs, bones and tissue.

10. The method of claim 1, further comprising dividing said model into voxels.

11. The method of claim 10, wherein said step of deriving said score comprises deriving said score for each of said voxels in said planning target volume.

12. The method of claim 11, wherein said treatment parameter comprises a radiation dose for each of said voxels.

13. The method of claim 12, wherein deriving said score comprises computing for said voxels an empiric score S_i:

$S_i=\frac{1}{N_T}<br><br>\underset{n\in <br><br>\mathrm{target}}{\sum <br><br>}<br><br>{\left(\frac{d_{\mathrm{ni}}}{D_T^P}\right)}^2,$

where d_ni is said radiation dose delivered to voxel n by beamlet i with its intensity set to the maximum without exceeding said tolerance dose of said at least one structure at risk, N_T is the number of voxels in said planning target volume, and D_T^P is a prescribed radiation dose.

14. The method of claim 12, wherein said score comprises a function selected from the group consisting of linear ranking functions and biological-modeling based ranking functions.

15. The method of claim 1, further comprising calculating a ratio by which the intensity of each beamlet has to be reduced to not exceed said tolerance parameter in said at least one structure at risk.

16. The method of claim 15, wherein said tolerance parameter is a radiation dose.

17. The method of claim 1, wherein said angle comprises an angle selected from the group consisting of gantry angles and couch angles.

18. The method of claim 1, further comprising selecting at least one of the parameters from the group consisting of collimator angles of said beamlets and energies of said beamlets based on said scoring function.

19. A storage medium tangibly embodying a method for selecting an orientation of a treatment beam in intensity modulated radiation therapy, said method comprising:

a) obtaining a model of a patient geometry comprising a planning target volume and at least one structure at risk;

b) assigning a tolerance parameter to said at least one structure at risk;

c) subdividing said treatment beam into beamlets;

d) selecting a treatment parameter;

e) selecting a set of angles for said treatment beam;

f) deriving a score for each angle of said set of angles by weighting each of said beamlets to maximize said treatment parameter in said planning target volume while not exceeding said tolerance parameter in said at least one structure at risk;

g) constructing a scoring function comprising said score as a function of angle; and

h) displaying said scoring function to an operator.