Time-resolved pre-treatment portal dosimetry systems, devices, and methods

• US 9,242,120 B2
• Filed: 06/22/2015
• Issued: 01/26/2016
• Est. Priority Date: 11/07/2013
• Status: Active Grant

• Current Assignee: Siemens Healthineers International AG
• Original Assignee: Varian Medical Systems International AG (Siemens AG)
• Inventors: Verhaegen, Frans, Podesta, Mark, Nijsten, Sebastiaan M. J. J. G., Persoon, Lucas C. G. G., Baltes, Christof, Scheib, Stefan G.
• Primary Examiner(s): NGUYEN, KIET TUAN
• Application Number:
  US14/745,829
• Publication Number:
  US 20150314140A1
• Time in Patent Office: 218 Days
• Field of Search: 378/65, 378/62, 382/132
• US Class Current: 1/1
• CPC Class Codes: A61N 2005/1054 using a portal imaging system
• CPC Class Codes: A61N 5/1031 using a specific method of dose optimization
• CPC Class Codes: A61N 5/1047 with movement of the radiation head during application of radiation, e.g. for intensity modulated arc therapy or IMAT
• CPC Class Codes: A61N 5/1071 for verifying the dose delivered by the treatment plan
• CPC Class Codes: A61N 5/1075 for testing, calibrating, or quality assurance of the radiation treatment apparatus

Abstract

Systems, devices, and methods for pre-treatment verification of radiation dose delivery in arc-based radiation therapy devices using a time-dependent gamma evaluation method.

Claims

1. A dosimetric evaluation method, comprising:

generating a sequence of portal dose images, the portal dose images in the sequence corresponding to measured radiation doses delivered according to a radiation treatment plan;

comparing the portal dose images generated with corresponding predicted portal dose images using a time-dependent gamma evaluation method; and

evaluating radiation dose delivery based on the comparison.

2. The method of claim 1, wherein the measured radiation doses are delivered at predetermined time intervals of the radiation treatment plan, and the comparing includes comparing the portal dose images generated for respective time intervals with corresponding predicted portal dose images.

3. The method of claim 2, wherein the time intervals correspond to respective control points (CPs) of the radiation treatment plan.

4. The method of claim 1, wherein the comparing comprises using the time-dependent gamma evaluation method to calculate dose differences, spatial differences, and time differences between points in the measured portal dose images and corresponding points in the predicted portal dose images.

5. The method of claim 1, wherein the evaluating includes determining dose delivery errors.

6. A method for verifying quantities of interest of a delivered radiation beam, comprising:

acquiring portal dose images during radiation beam delivery;

resampling the acquired portal dose images into respective time divisions corresponding to a radiation treatment plan'"'"'s control points (CPs) to obtain a sequence of measured portal dose images, the measured portal dose images in the sequence corresponding to respective control points (CPs);

comparing the measured portal dose images in the sequence with corresponding predicted portal dose images using a time-dependent gamma evaluation method; and

determining dose delivery errors based on the comparison.

7. The method of claim 6, wherein the comparing comprises using the time-dependent gamma evaluation method to calculate dose differences, spatial differences, and time differences between points in the measured portal dose images and corresponding points in the predicted portal dose images.

8. The method of claim 7, wherein the comparing includes computing a time-dependent gamma error matrix based on a gamma error function including time as a fourth dimension.

9. The method of claim 6, wherein the evaluating includes determining dose delivery errors.

10. A system for verifying a quantity of interest of a radiation beam, comprising:

a portal imaging device configured to measure incident radiation dose from predetermined radiation fields and to generate a series of portal dose images; and

a processing device operably connected to the portal dose imaging device and configured to store the series of portal dose images in a first data array having spatial locations and time of delivery of the predetermined radiation fields as dimensions, the processing device being further configured to store a series of predicted portal dose images in a second data array having spatial locations and time of delivery of predicted radiation fields as dimensions,

wherein the processing device is further configured to compare points in the first data array with corresponding points in the second data array using a 4D gamma evaluation method, the gamma evaluation method including dose differences, spatial differences, and time differences between corresponding points in the first and second data arrays as parameters, and

wherein errors in the quantities of interest are determined based on the comparison.

11. The system of claim 10, wherein the quantity of interest is of a radiation beam used in an arc-field radiation therapy device.

12. The system of claim 11, wherein the arc-field radiation therapy device is one of an intensity modulated radiation therapy device and a volumetric modulated arc therapy device.

13. The system of claim 10, wherein the portal imaging device is an electronic portal imaging device (EPID).

14. The system of claim 10, wherein the quantity of interest is radiation dose.

15. A system including a radiation therapy device and a computer processing system which executes a sequence of programmed instructions embodied on a computer-readable storage medium to cause the computer processing system to:

initiate radiation beam delivery in the radiation therapy device according to a radiation treatment delivery plan;

acquire portal dose images during the radiation beam delivery;

resample the portal dose images into respective time divisions corresponding to the radiation treatment plan'"'"'s control points (CPs) to obtain a sequence of measured portal dose images, each measured portal dose image in the sequence corresponding to a respective control point (CP);

compare the measured portal dose images in the sequence with corresponding predicted portal dose images using a time-dependent gamma evaluation method; and

determine radiation dose delivery errors based on the comparison.

16. The system of claim 15, wherein the time-dependent gamma evaluation method includes a 4D evaluation method including time as the fourth dimension.

17. The system of claim 15, wherein the comparing comprises using the time-dependent gamma evaluation method to calculate dose differences, spatial differences, and time differences between points in the measured portal dose images and corresponding points in the predicted portal dose images as parameters.

18. The system of claim 17, further including storing the predicted portal dose images as a first data set including positional information and time information of the points in the predicted portal dose images as parameters, and storing the measured portal dose images as a second data set including positional information and time information of the points in the measured portal dose images as parameters.

19. The system of claim 18, wherein the positional information includes spatial locations of the predicted and measured radiation fields, and the time information includes the times of the predicted and measured radiation fields, and wherein the comparing includes comparing the first and second data sets using the time-dependent gamma evaluation method.

20. The system of claim 19, wherein the comparing includes computing a time-dependent gamma error matrix based on a gamma error function: