Monitor units calculation method for proton fields

• US 7,987,053 B2
• Filed: 05/30/2008
• Issued: 07/26/2011
• Est. Priority Date: 05/30/2008
• Status: Active Grant

• Current Assignee: Siemens Healthineers International AG
• Original Assignee: Varian Medical Systems International AG (Siemens AG)
• Inventors: Schaffner, Barbara Ursula
• Primary Examiner(s): Charioui; Mohamed
• Assistant Examiner(s): Desta; Elias
• Application Number:
  US12/130,770
• Publication Number:
  US 20090299634A1
• Time in Patent Office: 1,152 Days
• Field of Search: 702/1, 702/179, 702/189, 382/128, 250/281, 250/286, 250/289, 128/922
• US Class Current: 702/1
• CPC Class Codes: A61N 2005/1087 Ions; Protons
• CPC Class Codes: A61N 5/1048 Monitoring, verifying, controlling systems and methods

Abstract

A method for determining a monitor unit that is associated with a process using ions, includes obtaining a depth dose curve, determining a characteristic parameter based on the depth dose curve, and using the characteristic parameter to determine a first monitor unit factor. A system for determining a monitor unit that is associated with a process using protons, includes a processor that is configured for obtaining a depth dose curve, determining a characteristic parameter based on the depth dose curve, and using the characteristic parameter to determine a first monitor unit factor.

Claims

1. A method for determining a monitor unit that is associated with a process using ions, comprising:

obtaining a depth dose curve;

determining a characteristic parameter based on the depth dose curve;

using the characteristic parameter to determine a first monitor unit factor for a first layer that is associated with a first feature of a range modulator; and

storing the first monitor unit factor in a device having a non-transitory medium;

wherein the act of using the characteristic parameter to determine the first monitor unit factor is performed by a processor.

2. The method of claim 1, wherein the depth dose curve is obtained by measurement.

3. The method of claim 1, wherein the depth dose curve is a model.

4. The method of claim 3, further comprising fitting the model to a measured depth dose curve.

5. The method of claim 1, further comprising applying a correction factor to the characteristic parameter.

6. The method of claim 5, wherein the correction factor is based on an entrance dose.

7. The method of claim 5, wherein the correction factor is a ratio of an entrance dose for a nozzle equivalent thickness associated with a layer, to an entrance dose for a reference nozzle equivalent thickness.

8. The method of claim 5, wherein the correction factor is based on a fluence at an isocenter.

9. The method of claim 5, wherein the correction factor is a ratio of a fluence at isocenter for a reference nozzle equivalent thickness, to a fluence at isocenter for a nozzle equivalent thickness associated with a layer.

10. The method of claim 5, wherein the correction factor is a function of entrance dose, fluence at isocenter, nozzle equivalent thickness associated with a layer, and a reference nozzle equivalent thickness.

11. The method of claim 5, wherein the correction factor is a correction for a ratio of values of an entrance dose at a monitor position and at an isocenter.

12. The method of claim 1, further comprising:

obtaining a second monitor unit factor for a second layer that is associated with a second feature of the range modulator; and

combining the first and second monitor unit factors to obtain a monitor unit.

13. The method of claim 12, wherein the monitor unit is obtained by:

applying a first weighted factor to the first monitor unit factor to obtain a first weighted monitor unit factor;

applying a second weighted factor to the second monitor unit factor to obtain a second weighted monitor unit factor; and

summing the first and second weighted monitor unit factors.

14. The method of claim 1, wherein the ions comprise protons.

35. The method of claim 1, wherein the range modulator is for reducing an energy of a beam, and has a step configuration.

36. The method of claim 12, wherein the first and second features comprise a first thickness and a second thickness, respectively, of the range modulator.

15. A system for determining a monitor unit that is associated with a process using ions, the system comprising a processor, wherein the processor is configured for:

obtaining a depth dose curve;

determining a characteristic parameter based on the depth dose curve; and

using the characteristic parameter to determine a first monitor unit factor for a first layer that is associated with a first feature of a range modulator.

16. The system of claim 15, wherein the depth dose curve is obtained by measurement.

17. The system of claim 15, wherein the depth dose curve is a model.

18. The system of claim 17, wherein the processor is further configured for fitting the model to a measured depth dose curve.

19. The system of claim 15, wherein the characteristic parameter comprises a normalization factor.

20. The system of claim 19, wherein the normalization factor is for converting a unit of dose in a model into another unit of dose.

21. The system of claim 15, further comprising applying a correction factor to the characteristic parameter.

22. The system of claim 21, wherein the correction factor is based on an entrance dose.

23. The system of claim 21, wherein the correction factor is a ratio of an entrance dose for a nozzle equivalent thickness associated with a layer, to an entrance dose for a reference nozzle equivalent thickness.

24. The system of claim 21, wherein the correction factor is based on a fluence at an isocenter.

25. The system of claim 21, wherein the correction factor is a ratio of a fluence at isocenter for a reference nozzle equivalent thickness, to a fluence at isocenter for a nozzle equivalent thickness associated with a layer.

26. The system of claim 21, wherein the correction factor is a function of entrance dose, fluence at isocenter, nozzle equivalent thickness associated with a layer, and a reference nozzle equivalent thickness.

27. The system of claim 21, wherein the correction factor is a correction for a ratio of values of an entrance dose at a monitor position and at an isocenter.

28. The system of claim 15, wherein the processor is further configured for:

further comprising;

obtaining a second monitor unit factor for a second layer that is associated with a second feature of the range modulator; and

combining the first and second monitor unit factors to obtain a monitor unit.

29. The system of claim 28, wherein the processor is configured to obtain the monitor unit by:

applying a first weighted factor to the first monitor unit factor to obtain a first weighted monitor unit factor;

applying a second weighted factor to the second monitor unit factor to obtain a second weighted monitor unit factor; and

summing the first and second weighted monitor unit factors.

30. The system of claim 15, wherein the ions comprise protons.

37. The system of claim 15, wherein the range modulator is for reducing an energy of a beam, and has a step configuration.

38. The system of claim 28, wherein the first and second features comprise a first thickness and a second thickness, respectively, of the range modulator.

31. A computer product having a set of instructions stored in a non-transitory medium, an execution of which causes a process to be performed, wherein the process is for determining a monitor unit that is associated with a process using ions, the process comprising:

obtaining a depth dose curve;

determining a characteristic parameter based on the depth dose curve; and

using the characteristic parameter to determine a first monitor unit factor for a first layer that is associated with a first feature of a range modulator.

32. The computer product of claim 31, wherein the process further comprises:

obtaining a second monitor unit factor for a second layer that is associated with a second feature of the range modulator; and

combining the first and second monitor unit factors to obtain a monitor unit.

33. The computer product of claim 32, the first and second features comprise a first thickness and a second thickness, respectively, of the range modulator.

34. The computer product of claim 31, wherein the range modulator is for reducing an energy of a beam, and has a step configuration.