Imaging-based self-adjusting radiation therapy systems, devices, and methods

Patent metadata

Field	Value
Publication number	US-9844358-B2
Application number	US-201414296233-A
Country	US
Kind code	B2
Filing date	Jun 4, 2014
Priority date	Jun 4, 2014
Publication date	Dec 19, 2017
Grant date	Dec 19, 2017

Abstract

Systems, devices, and methods are presented for automatic tuning, calibration, and verification of radiation therapy systems comprising control elements configured to control parameters of the radiation therapy systems based on images obtained using electronic portal imaging devices (EPIDs) included in the radiation therapy system.

First claim

The invention claimed is:

1. A method for calibrating a radiation treatment device, the radiation treatment device including control elements configured to control parameters of the radiation treatment device, the method comprising:
(i) acquiring, using an imaging device, one or more images representing beam fields produced by a beam source;
(ii) determining a parameter of the radiation treatment device from the one or more images, the parameter relating to an output of a control element;
(iii) evaluating the parameter against a predefined standard;
(iv) adjusting the output of the control element based on the result of the evaluating until the parameter meets the predefined standard; and
(v) repeating steps (i) through (iv) until the parameters are evaluated and the outputs of the control elements are adjusted,
wherein one of the parameters to be evaluated is the imaging device position from the beam source, the evaluating including:
acquiring a first and a second image in (i) with the imaging device positioned at two different locations; and
calculating the distance of the imaging device from the beam source based on an amount by which the imaging device was moved between the two locations, and a size of the beam field at the first location of the imaging device, and a size of the beam field at the second location of the imaging device.

2. The method of claim 1 , wherein the adjusting is automatic.

3. The method of claim 1 , wherein the adjusting is a combination of automatic and manual.

4. The method of claim 1 , wherein the adjusting is iterative.

5. The method of claim 1 , wherein the adjusting includes repeating steps (i) through (iii) after an initial adjustment.

6. The method of claim 5 , wherein the repeating is automatic.

7. The method of claim 1 , wherein the acquiring of the one or more images includes acquiring alternating image pairs, where each image pair includes a dark field followed by a flood field image.

8. The method of claim 1 , wherein the one or more images are acquired using one of an electronic portal imaging device (EPID) and a modified electronic portal imaging device (modified EPID).

9. The method of claim 8 , wherein in the modified EPID a scintillator layer is directly exposed to the beam from the beam source.

10. The method of claim 8 , wherein in the modified EPID a scintillator layer is exposed to the beam through an optical grade plastic cover.

11. The method of claim 10 , wherein the modified EPID further includes a collimating filter to alleviate off-axis external light sources.

12. The method of claim 8 , further comprising applying a correction map to the images acquired to convert the images into beam profiles.

13. The method of claim 1 , wherein the beam source is one of a radiation beam source, an electron-beam source, and a light field source.

14. The method of claim 1 , wherein the beam fields include an X-ray field, an electron-beam field, or a light field.

15. The method of claim 1 , wherein the parameters include beam symmetry, beam flatness, beam energy, beam asymmetry, beam alignment, beam dose linearity, beam field size, beam position, beam shape, and collimator position from isoplane.

16. The method of claim 1 , wherein the determining of the imagine device position from the beam source includes:
calculating the first location of the imaging device from the first image and the second location of the imaging device from the second image; and
calculating the distance (Z) of the imager from the beam source using

Z
=

∂
Z

D
B

D
A

-
1

,

where, ∂Z is the amount by which the imaging device was moved between the two locations, D A is the size of the beam field at the first location of the imaging device, and D B is the size of the beam field at the second location of the imaging device.

17. The method of claim 15 , wherein determining collimator position from isoplane includes:
calculating collimator position from a first image acquired at a first location of a collimator of the radiation treatment device and from a second image acquired at a second location of the collimator; and
determining projected distances of the collimator on the isoplane from the calculated collimator positions using an edge-detection method and a best-fit line algorithm.

18. The method of claim 17 , wherein the edge-detection method includes:
calculating a plurality of estimated edge points;
creating edge profiles for the edge points;
calculating edge point values for the edge profiles; and
calculating best-fit edge to populate the edge points.

19. The method of claim 15 , wherein determining beam symmetry includes:
acquiring a series of alternating dark field/flood field image pairs in (i);
generating a beam profile from the series of alternating dark field/flood field image pairs; and
calculating beam symmetry from the beam profile using one of a 2-Point difference, Area (2D), 2D slope deviation, Volume (3D), 2D centroid, and 3D centroid symmetry calculation algorithms.

20. The method of claim 15 , wherein determining beam position includes determining beam coincidence with an axis of rotation of a collimator of the radiation treatment device and includes:
acquiring a first integrated image at a first collimator aperture while the collimator is rotated through a first rotation angle, and acquiring a second integrated image at a second collimator aperture while the collimator is rotated through a second rotation angle in step (i);
determining a center of the first integrated image and a center of the second integrated image; and
calculating difference between the first and second image centers.

21. The method of claim 20 , wherein the calculating includes applying an edge-detection and best-fit circle algorithm.

22. The method of claim 15 , wherein determining beam position includes determining beam coincidence with an axis of rotation of a collimator of the radiation treatment device and includes:
inserting a collimating device into the beam path, the collimating device including a first and a second coaxial cone allowing the beam to pass therethrough;
acquiring a plurality of images at a plurality of collimator positions;
measuring a position of a center of the first cone and a position of a center of the second cone for an acquired image;
calculate a best fit circle for center positions of the first cone and for center positions of the second cone;
calculate a difference between a center of the best fit circle for the first cone and a center of the best fit circle for the second cone; and
determine a shift in the position of the beam source from the axis of rotation of the collimator based on the calculated difference.

23. The method of claim 15 , wherein determining beam flatness includes:
converting an image acquired in (i) to a beam profile; and
calculating flatness from the

Assignees

• Varian Med Sys Inc
• Varian Medical Systems Int Ag

Inventors

• Wiggers Robert T
• Leung Daryl
• Filiberti Reto W
• Morf Daniel
• Kung Diana
• Gaudio Stephen

Classifications

• A61B6/583

  using calibration phantoms · CPC title

• A61B6/547

  involving tracking of position of the device or parts of the device · CPC title

• A61N2005/1054

  using a portal imaging system · CPC title

• A61B6/586

  Detection of faults or malfunction of the device · CPC title

• A61N2005/1061

  using an x-ray imaging system having a separate imaging source · CPC title