Method for pre treatment verification in radiation therapy

• US 20060203967A1
• Filed: 05/21/2004
• Published: 09/14/2006
• Est. Priority Date: 05/23/2003
• Status: Active Grant

• Current Assignee: Gorgen Nilsson
• Original Assignee: Gorgen Nilsson
• Inventors: Nilsson, Gorgen
• Granted Patent: US 7,371,007 B2
• Time in Patent Office: Days
• US Class Current: 378/207
• CPC Class Codes: A61B 6/542 involving control of exposure
• CPC Class Codes: A61B 6/583 using calibration phantoms
• CPC Class Codes: A61N 2005/1076 using a dummy object placed in the radiation field, e.g. phantom
• CPC Class Codes: A61N 5/1048 Monitoring, verifying, controlling systems and methods

Abstract

The present invention relates to a method to measure dose distribution in a patient-shaped phantom with high accuracy. The invention consists of a method of measuring dose distribution in a phantom for radiation therapy treatment verification, a detector configuration in such a phantom, detector improvement and measurement methodology to enable application of correction factors in an accurate way.

Claims

1. Method of measuring dose distribution in a phantom for radiation therapy treatment verification, wherein at least two detector planes are arranged in said phantom in a non-parallel manner, each plane being provided with a plurality of diode detectors, wherein said phantom is irradiated using a patient specific treatment, comprising the steps of

obtaining information regarding the dose distribution inside said phantom by performing measurements using said detectors;

dividing the measurements in time-intervals, each time-interval having maximum length of approximately 100 msec; and

using said information in the treatment verification.

2. Method according to claim 1, wherein the information obtained by means of said measurements is used for IMRT verification.

3. Method according to claim 1, wherein said irradiation of the phantom comprises delivering dose pulses, further comprising the step of synchronizing the measurements with said delivered doses.

4. Method according to claim 1, further comprising the steps of:

synchronizing the measurements with a respiratory cycle of the patient for which the patent specific treatment is intended; and

determining the dose delivered in the various phases of the respiratory cycle.

5. Method according to claim 1, further comprising the step of storing the data for each specific time-interval for measurements in said phantom.

6. Method according to claim 1, further comprising the step of calculating correction factors for each time-interval using said obtained information regarding the dose distribution inside said phantom.

7. Method according to claim 6, wherein the correction factors are calculated according to

Corn,f,seg-n,p,t(i),t(i+1)=Cdir*Cdepth*Cpos

where

Corrn, f, seg-n, p, t(i), t(i+1) The correction factor to be used with detector element n, in the sub field f in the phantom, correcting the measured dose integrated from time t(i) until t(i+1) to achieve the dose in the point of location of detector n

Cdir Factor correcting for any directional dependence in detector n

Cdepth Factor correcting for any depth (energy and/or dose rate) in detector n

Cpos Factor correcting for any position (in primary beam, outside primary beam, edge of primary beam, etc.) dependency in detector n.

8. Method according to claim 6, wherein the correction factors are calculated according to

Corrn,f,seg-n,p,t(i),t(i+1)=Cdir+Cdepth+Cpos

where

Corn, f, seg-n, p, t(i), t(i+1) The correction factor to be used with detector element n, in the sub field f in the phantom, correcting the measured dose integrated from time t(i) until t(i+1) to achieve the dose in the point of location of detector n

Cdir Factor correcting for any directional dependence in detector n

Cdepth Factor correcting for any depth (energy and/or dose rate) in detector n

Cpos Factor correcting for any position (in primary beam, outside primary beam, edge of primary beam, etc.) dependency in detector n.

9. Method according to claim 1, wherein the detector planes are arranged such that for each gantry angle projection, either of said non-parallel planes intersects with all parts of the radiation beam or sub-beams.

10. Method according to claim 1, wherein each detector plane is provided with detectors having a thickness in a range less than the range of the electrons of the maximum energy in the range where the dependency is significant.

14. Use of a detector configuration arranged in a phantom suitable for radiation therapy in a method according to claim 1, said configuration comprising at least two detector planes provided with a plurality of diode detectors for measuring irradiation in said phantom, said irradiation being delivered using a patient specific treatment, wherein said planes being arranged in a non-parallel manner, wherein said detectors has a thickness in a range less than the range of the electrons of the maximum energy in the range where the dependency is significant.

15. Detector configuration according to claim 14, wherein said non-parallel planes are arranged such that, for each gantry angel projection, either of said planes intersects with all parts of the radiation beam or sub-beams.

16. Use of a diode detector arranged with a thickness in a range less than the range of the electrons of the maximum energy in the range where the dependency is significant in a method according to claim 1.

17. Diode detector according to claim 16, wherein said detector is used in water phantom dosimetry or in vivo dosimetry during Brachy therapy in Radio therapy.

18. Computer readable medium comprising instructions for bringing a computer to perform the steps of the method according to claim 1.

11. Method of measuring dose distribution in a phantom for radiation therapy treatment verification, wherein detector planes are arranged in said phantom, each plane being provided with a plurality of diode detectors, wherein said phantom is irradiated using a patient specific treatment, comprising the steps of

obtaining information regarding the dose distribution inside said phantom by performing measurements using said detectors;

dividing the measurements in time-intervals, each time-interval having maximum length of approximately 100 msec;

synchronizing the measurements with a respiratory cycle of the patient for which the patent specific treatment is intended;

determining the dose delivered in the various phases of the respiratory cycle; and

using said information in the treatment verification.

12. Method according to claim 11, wherein at least two detector planes are arranged in said phantom in a non-parallel manner.

13. (canceled)