Adaptive x-ray control

• US 20070189455A1
• Filed: 02/14/2006
• Published: 08/16/2007
• Est. Priority Date: 02/14/2006
• Status: Abandoned Application

• Current Assignee: Accuray Incorporated
• Original Assignee: Accuray Incorporated
• Inventors: Allison, John
• Application Number:
  US11/354,411
• Publication Number:
  US 20070189455A1
• Time in Patent Office: Days
• US Class Current: 378/95
• CPC Class Codes: A61B 2090/364 Correlation of different images or relation of image positions in respect to the body
• CPC Class Codes: A61B 5/7285 for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence
• CPC Class Codes: A61B 6/00 Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment instruments measuring radiation intensity for application in the field of nuclear medicine, e.g. in vivo counting, G01T1/161; apparatus for taking X-ray photographs G03B42/02
• CPC Class Codes: A61B 6/022 Stereoscopic imaging
• CPC Class Codes: A61B 6/4458 the source unit or the detector unit being attached to robotic arms
• CPC Class Codes: A61B 6/5217 extracting a diagnostic or physiological parameter from medical diagnostic data
• CPC Class Codes: A61B 6/541 involving acquisition triggered by a physiological signal
• CPC Class Codes: A61B 6/542 involving control of exposure
• CPC Class Codes: A61B 6/544 dependent on patient size
• CPC Class Codes: A61B 8/543 involving acquisition triggered by a physiological signal
• CPC Class Codes: A61N 2005/1061 using an x-ray imaging system having a separate imaging source
• CPC Class Codes: A61N 2005/1062 using virtual X-ray images, e.g. digitally reconstructed radiographs [DRR]
• CPC Class Codes: A61N 5/103 Treatment planning systems
• CPC Class Codes: A61N 5/1048 Monitoring, verifying, controlling systems and methods
• CPC Class Codes: G16H 50/30 for calculating health indices; for individual health risk assessment

Abstract

A method, apparatus and system for measuring the signal-to-noise ratio of x-ray images and to adaptively control x-ray exposure in response to image quality and patient movement.

Claims

1. A method, comprising:

measuring a signal-to-noise ratio (SNR) of an x-ray image generated with an x-ray source; and

adaptively adjusting an output of the x-ray source based on the SNR of the x-ray image.

2. The method of claim 1, wherein adaptively adjusting the output of the x-ray source comprises:

increasing the output to increase the SNR if the SNR is less than a lower SNR threshold; and

decreasing the output to decrease the SNR if the SNR is greater than an upper SNR threshold.

3. The method of claim 2, further comprising:

adjusting the output for subsequent x-ray images in response to patient movement to maintain the SNR between lower SNR threshold and the upper SNR threshold.

4. The method of claim 2, wherein adjusting the output of the x-ray source comprises adjusting at least one of an energy level of the x-ray source and an operating duration of the x-ray source.

5. The method of claim 2, wherein adjusting the output of the x-ray source is performed automatically.

6. The method of claim 2, further comprising requesting authorization from a system operator before adjusting the output of the x-ray source.

7. The method of claim 2, further comprising:

acquiring subsequent x-ray images with an image acquisition process that adapts to patient movement.

8. The method of claim 7, wherein the image acquisition process comprises:

comparing sequential x-ray images to detect patient movement; and

adjusting time intervals between subsequent x-ray images in response to the patient movement.

9. The method of claim 8, wherein adjusting the time intervals comprises:

increasing the time intervals between the subsequent x-ray images when the patient movement decreases; and

decreasing the time intervals between the subsequent x-ray images when the patient movement increases.

10. The method of claim 9, wherein the image acquisition process comprises:

adjusting a total number of x-ray images taken during an image-guided radiation treatment session in response to patient movement.

11. The method of claim 10, wherein adjusting the total number of x-ray images comprises:

decreasing the total number of x-ray images taken during the image-guided radiation treatment session when the time intervals between the subsequent x-ray images have been increased in response to the patient movement; and

increasing the total number of x-ray images taken during the image-guided radiation treatment session when the time intervals between the subsequent x-ray images have been decreased in response to the patient movement.

12. The method of claim 10, further comprising:

adjusting a radiation treatment dose to compensate for a change in imaging x-ray exposure due to adjustments to the total number of x-ray images and the output of the x-ray source in response to the patient movement, wherein the radiation treatment dose is at least one of a current treatment fraction and a future treatment fraction.

13. The method of claim 11, further comprising:

decreasing the output level of the x-ray source to maintain a cumulative radiation exposure level below a cumulative radiation exposure limit when the total number of x-ray images taken during the image-guided radiation treatment session is increased.

14. The method of claim 7, wherein the image acquisition process comprises:

adjusting a ratio of x-ray images to treatment nodes in response to patient movement.

15. The method of claim 14, wherein adjusting the ratio comprises:

decreasing the ratio of x-ray images to treatment nodes when the patient movement is less than an amount of movement or movement variance assumed during a treatment planning phase; and

increasing the ratio of x-ray images to treatment nodes when the patient movement is greater than the amount of movement or movement variance assumed during the treatment planning phase.

16. The method of claim 15, wherein each treatment node comprises one or more treatment paths, wherein the image acquisition process further comprises:

adjusting a ratio of the x-ray images to the treatment paths in response to patient movement.

17. The method of claim 7, further comprising:

detecting patient movement during an image-guided radiation treatment session; and

triggering the acquisition of x-ray images in response to patient movement greater than a displacement that exceeds a targeting accuracy threshold.

18. The method of claim 17, wherein detecting patient movement comprises at least one of:

comparing sequential x-ray images;

monitoring the patient with a machine vision system;

reading a strain gauge attached to the patient; and

laser-scanning a 3-D contour of the patient.

19. A system comprising:

an imaging system including an x-ray source to generate x-ray images; and

a processing device to control the imaging system, wherein the processing device is configured to

measure a signal-to-noise ratio (SNR) of an x-ray image generated with an x-ray source; and

adaptively adjust an output of the x-ray source based on the SNR of the x-ray image.

20. The system of claim 19, wherein to adjust the output of the x-ray source, the processing device is configured to:

increase the output to increase the SNR if the SNR is less than a lower SNR threshold; and

decrease the output to decrease the SNR if the SNR is greater than an upper SNR threshold.

21. The system of claim 20, wherein the processing device is further configured to:

adjust the output for subsequent x-ray images in response to patient movement to maintain the SNR between lower SNR threshold and the upper SNR threshold.

22. The system of claim 19, wherein the output of the x-ray source comprises an energy level and a duration, and wherein to adjust the output of the x-ray source, the processing device is configured to adjust at least one of the energy level and the duration.

23. The system of claim 22, wherein the processing device is configured to adjust the output level automatically without operator intervention.

24. The system of claim 22, wherein the processing device is configured to obtain authorization from an operator to adjust the output level of the x-ray source.

25. The system of claim 20, wherein the imaging system is further configured, under control of the processing device to:

acquire subsequent x-ray images with an image acquisition process that adapts to patient movement.

26. The system of claim 25, wherein the processing device is configured to:

compare sequential x-ray images to detect patient movement; and

to

adjust time intervals between subsequent x-ray images in response to the patient movement.

27. The system of claim 26, wherein to adjust time intervals the processing device is configured to:

increase the time intervals between the subsequent x-ray images when the patient movement decrease; and

to

decrease the time intervals between the subsequent x-ray images when the patient movement increases.

28. The system of claim 25, wherein the processing device is further configured to:

adjust a total number of x-ray images taken during an image-guided radiation treatment session in response to patient movement.

29. The system of claim 28, wherein to adjust the total number of x-ray images the processing device is configured to:

decrease the total number of x-ray images taken during the image-guided radiation treatment session when the time intervals between the subsequent x-ray images have been increased in response to the patient movement; and

to increase the total number of x-ray images taken during the image-guided radiation treatment session when the time intervals between the subsequent x-ray images have been decreased in response to the patient movement.

30. The system of claim 27, further comprising a radiation delivery system to deliver a radiation treatment dose, wherein the processing device is further configured to adjust the radiation treatment dose to compensate for a change in imaging x-ray exposure due to adjustments to the total number of x-ray images and the output of the x-ray source in response to the patient movement, wherein the radiation treatment dose is at least one of a current treatment fraction and a future treatment fraction.

31. The system of claim 29, wherein the processing device is further configured to:

decrease the output level of the x-ray source to maintain a cumulative radiation exposure level below a cumulative radiation exposure limit when the total number of x-ray images taken during the image-guided radiation treatment session is increased.

32. The system of claim 31, wherein the processing device is further configured to:

adjust a ratio of x-ray images to treatment nodes in response to the patient movement.

33. The system of claim 32, wherein to adjust the ratio the processing device is configured to:

decrease the ratio when the patient movement is less than an amount of movement or movement variance assumed during a treatment planning phase; and

to

increase the ratio when the patient movement is greater than the amount of movement or movement variance assumed during the treatment planning phase.

34. The system of claim 33, wherein each treatment node comprises one or more treatment paths, and wherein the processing device is further configured to:

adjust a ratio of the x-ray images to the treatment paths in response to the patient movement.

35. The system of claim 25, wherein the processing device is further configured to:

detect patient movement during an image-guided radiation treatment session;

interrupt the radiation treatment and trigger the acquisition of x-ray images if the patient movement is greater than a displacement that exceeds a targeting accuracy threshold.

36. An article of manufacture comprising:

a machine-accessible medium including data that, when accessed by a machine, cause the machine to perform operations comprising;

measuring a signal-to-noise ratio (SNR) of an x-ray image generated with an x-ray source; and

adaptively adjusting an output of the x-ray source based on the SNR of the x-ray image.

37. The article of manufacture of claim 36, wherein the operation of adaptively adjusting the output level of the x-ray source comprises:

increasing the output to increase the SNR if the SNR is less than a lower SNR threshold; and

decreasing the output to decrease the SNR if the SNR is greater than an upper SNR threshold.

38. The article of manufacture of claim 37, wherein the machine-accessible medium further includes data that cause the machine to perform operations comprising:

adjusting the output for subsequent x-ray images in response to patient movement to maintain the SNR between lower SNR threshold and the upper SNR threshold.

39. The article of manufacture of claim 37, wherein the operation of adjusting the output of the x-ray source comprises adjusting at least one of an energy level of the x-ray source and an operating duration of the x-ray source.

40. The article of manufacture of claim 37, wherein the operation of adjusting the output of the x-ray source is performed automatically without operator intervention.

41. The article of manufacture of claim 37, wherein the machine-accessible medium further includes data that cause the machine to perform operations comprising:

requesting authorization from a system operator before adjusting the output of the x-ray source.

42. The article of manufacture of claim 37, wherein the machine-accessible medium further includes data that cause the machine to perform operations comprising:

acquiring subsequent x-ray images with an image acquisition process that adapts to patient movement.

43. The article of manufacture of claim 42, wherein the operation of acquiring subsequent x-ray images comprises:

comparing sequential x-ray images to detect patient movement; and

adjusting time intervals between the subsequent x-ray images in response to the patient movement.

44. The article of manufacture of claim 43, wherein the operation of adjusting time intervals between the subsequent x-ray images in response to the patient movement comprises:

increasing the time intervals between the subsequent x-ray images when the patient movement decreases; and

decreasing the time intervals between the subsequent x-ray images when the patient movement increases.

45. The article of manufacture of claim 44, wherein the machine-accessible medium further includes data that cause the machine to perform operations comprising:

adjusting a total number of x-ray images taken during an image-guided radiation treatment session in response to the patient movement.

46. The article of manufacture of claim 45, wherein the operation of adjusting the total number of x-ray images taken during the image-guided radiation treatment session in response to the patient movement comprises:

decreasing the total number of x-ray images taken during the image-guided radiation treatment session when the time intervals between the subsequent x-ray images have been increased in response to the patient movement; and

increasing the total number of x-ray images taken during the image-guided radiation treatment session when the time intervals between the subsequent x-ray images have been decreased in response to the patient movement.

47. The article of manufacture of claim 45, wherein the machine-accessible medium further includes data that cause the machine to perform operations comprising:

adjusting a radiation treatment dose to compensate for a change in imaging x-ray exposure due to adjustments to the total number of x-ray images and the output of the x-ray source in response to the patient movement, wherein the radiation treatment dose is at least one of a current treatment fraction and a future treatment fraction.

48. The article of manufacture of claim 46, wherein the machine-accessible medium further includes data that cause the machine to perform operations comprising:

decreasing the output level of the x-ray source to maintain a cumulative radiation exposure level below a cumulative radiation exposure limit when the total number of x-ray images taken during the image-guided radiation treatment session is increased.

49. The article of manufacture of claim 42, wherein the machine-accessible medium further includes data that cause the machine to perform operations comprising:

adjusting a ratio of x-ray images to treatment nodes in response to the patient movement.

50. The article of manufacture of claim 49, wherein the operation of adjusting the ratio of x-ray images to treatment nodes in response to the patient movement comprises:

decreasing the ratio of x-ray images to treatment nodes when the patient movement is less than an amount of movement or movement variance assumed during a treatment planning phase; and

increasing the ratio of x-ray images to treatment nodes when the patient movement is greater than the amount of movement or movement variance assumed during the treatment planning phase.

51. The article of manufacture of claim 50, wherein each treatment node comprises one or more treatment paths, and wherein the machine-accessible medium further includes data that cause the machine to perform operations comprising:

adjusting a ratio of the x-ray images to the treatment paths in response to patient movement.

52. The article of manufacture of claim 42, wherein the machine-accessible medium further includes data that cause the machine to perform operations comprising:

detecting the patient movement during the image-guided radiation treatment session;

interrupting the image-guided radiation treatment session and triggering the acquisition of x-ray images if the patient movement is greater than a displacement that exceeds a targeting accuracy threshold.

53. The article of manufacture of claim 52, wherein the operation of detecting patient movement during the image-guided radiation treatment session comprises at least one of:

comparing sequential x-rays;

monitoring the patient with a machine vision system;

reading a strain gauge attached to the patient; and

laser-scanning a 3-D contour of the patient.

54. An apparatus, comprising:

means for measuring a signal-to-noise ratio (SNR) of an x-ray image generated with an x-ray source; and

means for adaptively adjusting an output of the x-ray source based on the SNR of the x-ray image.

55. The apparatus of claim 54, wherein the means for adaptively adjusting the output level of the x-ray source comprises:

means for increasing the output to increase the SNR if the SNR is less than a lower SNR threshold; and

means for decreasing the output to decrease the SNR if the SNR is greater than an upper SNR threshold.

56. The apparatus of claim 55, further comprising:

means for adjusting the output for subsequent x-ray images in response to patient movement to maintain the SNR between lower SNR threshold and the upper SNR threshold.

57. The apparatus of claim 55, further comprising:

means for acquiring subsequent x-ray images with an image acquisition process that adapts to patient movement.