Planning method and apparatus for radiation dosimetry

• US 6,393,096 B1
• Filed: 05/27/1999
• Issued: 05/21/2002
• Est. Priority Date: 05/27/1998
• Status: Expired due to Term

• Current Assignee: Best Medical International Incorporated (TeamBest Group)
• Original Assignee: Nomos Corporation (North American Scientific, Inc.)
• Inventors: Hill, Robert, Carol, Mark P., Nash, Richard, Curran, Bruce H.
• Primary Examiner(s): BRUCE, DAVID VERNON
• Application Number:
  US09/320,980
• Time in Patent Office: 1,090 Days
• Field of Search: 378/64, 378/65, 378/108, 378/151
• US Class Current: 378/65
• CPC Class Codes: A61N 5/1031 using a specific method of dose optimization

Abstract

A method and apparatus for determining an optimized radiation beam arrangement for applying radiation to a tumor target volume while minimizing radiation of a structure volume in a patient, comprising: using a computer to computationally obtain a proposed radiation beam arrangement; using the computer to computationally change the proposed radiation beam arrangement iteratively, incorporating a cost function at each iteration to approach correspondence of a CDVH associated with the proposed radiation beam arrangement to a CDVH associated with a pre-determined desired dose prescription; comparing the dose distribution to a prescribed dose for the tumor volume and surrounding tissue structures, and increasing or decreasing radiation beam intensity if the change of the proposed beam arrangement leads to a greater correspondence to the desired dose prescription to obtain an optimized radiation beam arrangement.

Claims

1. A method of determining an optimized radiation beam arrangement for applying radiation to a tumor target volume while minimizing radiation of a structure volume in a patient, comprising the steps of:

using a computer to computationally obtain a proposed radiation beam arrangement;

using a computer to computationally change the proposed radiation beam arrangement iteratively,

incorporating a cost function at each iteration to approach correspondence of a CDVH associated with the proposed radiation beam arrangement to a CDVH associated with a predetermined desired dose prescription;

comparing the dose distribution to a prescribed dose for the tumor volume and surrounding tissue structures, and

increasing or decreasing radiation beam intensity if the change of the proposed beam arrangement leads to a greater correspondence to the desired dose prescription to obtain an optimized radiation beam arrangement.

2. The method of claim 1, wherein the cost function is obtained by the steps of:

determining a CDVH associated with the desired dose prescription;

assigning zones to each CDVH;

assigning weights to each zone, applicable to the CDVHs associated with both the desired dose prescription and the proposed radiation beam arrangement;

calculating a zone cost for each target and each structure, according to the following formula;

${\mathrm{INF}}_1<br><br>\left(x,\mathrm{scale},\mathrm{base},\mathrm{offset}\right)=<br><br>\begin{array}{c}\mathrm{base}<br><br>\text{\hspace{1em}<br><br>}<br><br>x-{\mathrm{offset}}^3+\mathrm{scale}<br><br>\text{\hspace{1em}<br><br>}<br><br>x,\mathrm{if}<br><br>\text{\hspace{1em}<br><br>}<br><br>x/\ge <br><br>\mathrm{offset}\\ \mathrm{scale}<br><br>\text{\hspace{1em}<br><br>}<br><br>x,\mathrm{if}<br><br>\text{\hspace{1em}<br><br>}<br><br>x<<br><br>\mathrm{offset}\end{array}<br><br>,$

where x is a given control point value for a given pair CDVH curves;

offset is a predetermined value along an influence curve as a function of x, where the influence curve turns from linear to exponential;

scale is a predetermined value which controls the influence function up to a point along the influence curve at which x=offset; and

base is a predetermined value which controls the influence function beyond the point alone the influence curve at which x=offset.

3. The method of claim 1 or 2, wherein the proposed radiation beam arrangement is calculated using simulated annealing radiation therapy planning methods.

4. The method of claim 1 or 2, further comprising the step of applying the optimized radiation beam arrangement to the patient with a conformal radiation therapy apparatus.

5. The method of claim 3, further comprising the step of applying the optimized radiation beam arrangement to the patient with a conformal radiation therapy apparatus.

6. The method of claim 4, further comprising the step of applying the optimized radiation beam arrangement to the patient with a conformal radiation therapy apparatus.

7. The method of claim 1, wherein the CDVH associated with the predetermined desired dose prescription is computationally constructed by the computer based on partial volume data associated with the predetermined desired dose prescription entered into the computer.

8. The method of claim 1, wherein the CDVH associated with the predetermined desired dose prescription is graphically entered into the computer.

9. The method of claim 2, wherein the CDVH associated with the predetermined desired dose prescription is computationally constructed by the computer based on partial volume data associated with the predetermined desired dose.

10. The method of claim 2, wherein the CDVH associated with the predetermined desired dose prescription is graphically entered into the computer.

11. The method of claim 1, wherein the cost function is obtained by the steps of:

determining a CDVH associated with the desired dose prescription;

assigning zones to each CDVH;

assigning weights to each zone, applicable to the CDVHs associated with both the desired dose prescription and the proposed radiation beam arrangement;

calculating a zone cost for each target and each structure, according to the following formula ${\mathrm{INF}}_2<br><br>\left(x,\mathrm{scale},\mathrm{base},\mathrm{offset}\right)=<br><br>\begin{array}{c}-\mathrm{scale}<br><br>\lfloor <br><br>\frac{{\left(x-\mathrm{offset}\right)}^2}{x-\mathrm{offset}+\mathrm{base}}\rfloor <br><br>+\mathrm{scale}<br><br>\left(x\right),\mathrm{if}<br><br>\text{\hspace{1em}<br><br>}<br><br>x\ge <br><br>\mathrm{offset}\\ \mathrm{scale}<br><br>\left(x\right),\mathrm{if}<br><br>\text{\hspace{1em}<br><br>}<br><br>x<<br><br>\mathrm{offset}\end{array}<br><br>$

where x is a given control point value for a given pair CDVH curves;

offset is a predetermined value along an influence curve as a functionof x, where the influence curve turns from linear to exponential;

scale is a predetermined value which controls the influence function up to a point along the influence curve at which x=offset; and

base is a predetermined value which controls the influence function beyond the point alone the influence curve at which x=offset value.

12. The method of claim 11, wherein the proposed radiation beam arrangement is calculated using simulated annealing radiation therapy planning methods.

13. The method of claim 11, further comprising the step of applying the optimized radiation beam arrangement to the patient with a conformal radiation therapy apparatus.

14. The method of claim 12, further comprising the step of applying the optimized radiation beam arrangement to the patient with a conformal radiation therapy apparatus.

15. The method of claim 13, further comprising the step of applying the optimized radiation beam arrangement to the patient with a conformal radiation therapy apparatus.

16. The method of claim 11, wherein the CDVH associated with the predetermined desired dose prescription is computationally constructed by the computer based on partial volume data associated with the predetermined desired dose.

17. The method of claim 14, wherein the CDVH associated with the predetermined desired dose prescription is graphically entered into the computer.

18. The method of claim 1, 2, or 14 further comprising the step of allowing a radiation limit on the tissue structure to be exceeded by a set amount if such excess allows better conformation to the desired target CDVH curve.

19. The method of claim 1, further comprising providing a user with a range of values to indicate the importance of each object of irradiation to the user.

20. The method of claim 1, further comprising providing a user with a range of values for conformality control.

21. A method of determining an optimized radiation beam arrangement for applying radiation to a tumor target volume while minimizing radiation of a structure volume in a patient, comprising the steps of:

(a) determining a desired CDVH associated with each target and structure;

(b) using a computer to iteratively compare a cost of a radiation beam arrangement proposed during a given iteration to a radiation beam arrangement proposed during the previous iteration based on the relative costs associated with the proposed radiation beam arrangement, the costs being calculated by;

(1) determining a CDVH associated with each target and structure based on the proposed radiation beam arrangement of a given iteration;

(2) assigning cost zones to the desired CDVH and the proposed CDVH of a given iteration associated with each target and structure;

(3) assigning a weight value to each cost zone of each CDVH associated with each target and structure;

(4) for each target and structure, multiplying the weight value of each zone by the quotient of a value representing the area of the zone of the CDVH associated with the proposed radiation beam arrangement and a value representing the area of the zone of the CDVH associated with the desired radiation beam arrangement;

(5) summing the results of step (4) for each zone of each CDVH of each target and structure to obtain a total dosage cost;

(c) increasing or decreasing radiation beam intensity if the change of the proposed beam arrangement leads to a greater correspondence to the desired dose prescription;

(d) allowing a radiation limit on the tissue structure to be exceeded by a set amount if such excess allows better conformation to the desired target CDVH curve; and

(e) repeating steps b through d until the proposed radiation beam arrangement has obtained an optimized radiation beam arrangement.

22. The method of claim 21, wherein the proposed radiation beam arrangement is calculated using simulated annealing radiation therapy planning methods.

23. The method of claim 21, further comprising the step of applying the optimized radiation beam arrangement to the patient using a conformal radiation therapy apparatus.

24. The method of claim 22, further comprising the step of applying the optimized radiation beam arrangement to the patient using a conformal radiation therapy apparatus.

25. A method of determining an optimized radiation beam arrangement for applying radiation to a tumor target volume while minimizing radiation of a structure volume in a patient, comprising the steps of:

using a computer to iteratively obtain a proposed radiation beam arrangement;

providing a user with a selective range of input values with an indication of the importance of the value in providing an optimized radiation beam arrangement; and

providing separate parameter profiles depending on the the user'"'"'s input value selection.

26. The method of claim 25, wherein the input value is an object to be irradiated.

27. The method of claim 25, wherein the input value is in units of conformality control.

28. The method of claim 25, wherein the proposed radiation beam arrangement is changed by changing the beam weights.

29. The method of claim 25, wherein the partial volume data is calculated by the computer based on a CDVH graphically entered into the computer using a pointing device.

30. The method of claim 25, wherein the partial volume data is entered directly into the computer.

31. Apparatus for determining an optimized radiation beam arrangement for applying radiation to a tumor target volume while minimizing radiation of a structure volume in a patient, comprising a computer which is adapted to:

(a) computationally obtain a proposed radiation beam arrangement,

(b) computationally change the proposed radiation beam arrangement iteratively to conform to a target CDVH curve,

(c) incorporate a cost function at each iteration to approach correspondence of partial volume data associated with the proposed radiation beam arrangement to partial volume data associated with a predetermined desired dose prescription,

(d) reject the change of the proposed radiation beam arrangement if the change of the proposed radiation beam arrangement leads to a lesser correspondence to the desired dose prescription and to accept the change of the proposed radiation beam arrangement if the change of the proposed radiation beam arrangement leads to a greater correspondence to the desired dose prescription to obtain an optimized radiation beam arrangement, and

(e) exceed the cost function by a set amount if such excess allows better conformation with the target CDHV curve.

32. The apparatus of claim 31, wherein the proposed radiation beam arrangement is changed by changing the beam weights.

33. The apparatus of claim 31, further comprising:

a conformal radiation therapy apparatus in communication with the computer for applying the optimized radiation beam arrangement to the patient.

34. Apparatus for determining an optimized radiation beam arrangement for applying radiation to a tumor target volume while minimizing radiation of a structure volume in a patient, comprising a computer, including:

means for computationally obtaining a proposed radiation beam arrangement;

means for computationally changing the proposed radiation beam arrangement iteratively to conform to a CDHV curve;

means for incorporating a cost function at each iteration to approach correspondence of partial volume data associated with the proposed radiation beam arrangement to partial volume data associated with a predetermined desired dose prescription;

means for rejecting the change of the proposed radiation beam arrangement if the change of the proposed radiation beam arrangement leads to a lesser correspondence to the desired dose prescription and accepting the change of the proposed radiation beam arrangement if the change of the proposed radiation beam arrangement leads to a greater correspondence to the desired dose prescription to obtain an optimized radiation beam arrangement; and

means for adapting the radiation beam arrangement to exceed the cost function by a set amount if such excess allows better conformation with the target CDHV curve.

35. The apparatus of claim 34, wherein the means for computationally changing the proposed radiation beam arrangement includes a means for changing the beam weights.

36. The apparatus of claim 34, further comprising a conformal radiation therapy apparatus in communication with the computer for applying the optimized radiation beam arrangement to the patient.

37. A method of determining an optimized radiation beam arrangement for applying radiation to at least one tumor target volume while minimizing radiation of at least one structure volume in a patient, comprising the steps of:

determining desired partial volume data for each of the at least one target volume and structure volume associated with a desired dose prescription;

entering the desired partial volume data into a computer;

in response to the desired partial volume data, using the computer to computationally approximate desired CDVHs for each of the at least one target and structure associated with the desired dose prescription; and

using the computer to computationally calculate the optimized radiation beam arrangement associated with the CDVHs approximated by the computer.

38. The method of claim 37, wherein the CDVHs approximated by the computer are approximated by the steps of:

using the computer to computationally obtain a set of proposed beam weights;

using the computer to computationally change the set of proposed beam weights iteratively, incorporating a cost function at each iteration to determine a cost of the change to the set of proposed beam weights; and

rejecting the change to the set of proposed beam weights if the change to the set of proposed beam weights leads to a lesser correspondence to the desired CDVHs and accepting the change to the set of proposed beam weights if the change to the set of proposed beam weights leads to a greater correspondence to the desired CDVHs.

39. The method of claim 38, wherein the optimized radiation beam arrangement is calculated using simulated annealing radiation therapy planning methods.

40. The method of claim 38, further comprising the step of applying the optimized radiation beam arrangement to the patient with a conformal radiation therapy apparatus.

41. The method of claim 38, wherein the desired CDVHs are computationally constructed by the computer based on numerical values representing the partial volume data entered into the computer.

42. The method of claim 37 or 38, wherein the desired CDVHs are computationally constructed by the computer based on numerical values representing the partial volume data entered into the computer.

43. A method of determining an optimized radiation beam arrangement for applying radiation to at least one tumor target volume while minimizing radiation to at least one structure volume in a patient, comprising the steps of:

distinguishing each of the at least one tumor target volume and each of the at least one structure volume by target or structure type;

determining desired partial volume data for each of the at least one target volume and structure volume associated with a desired dose prescription;

entering the desired partial volume data into a computer;

providing a user with a range of values to indicate the importance of objects to be irradiated;

providing the user with a range of conformality control factors; and

using the computer to computationally calculate an optimized radiation beam arrangement.

44. The method of claim 43, further comprising the step of applying the optimized radiation beam arrangement to the patient with a conformal radiation therapy apparatus.

45. The method of claim 43, wherein the target or structure types are distinguished as either Biologically Uniform or Biologically Polymorphic.

46. The method of claim 43, wherein the optimized radiation beam arrangement is calculated using different cost function parameters depending on the target or structure type.