Delivery modification system for radiation therapy

• US 6,385,286 B1
• Filed: 06/28/2000
• Issued: 05/07/2002
• Est. Priority Date: 08/06/1998
• Status: Expired due to Term

• Current Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Original Assignee: Wisconsin Alumni Research Foundation (University of Wisconsin System)
• Inventors: Fitchard, Edward E., Mackie, Thomas R., Reckwerdt, Paul J., Olivera, Gustavo H.
• Primary Examiner(s): DUNN, DREW A
• Application Number:
  US09/582,538
• Time in Patent Office: 678 Days
• Field of Search: 378/65, 378/8, 378/19, 378/20, 378/64, 378/69
• US Class Current: 378/65
• CPC Class Codes: A61N 5/1037 taking into account the movement of the target, e.g. 4D-image based planning
• CPC Class Codes: A61N 5/1042 with spatial modulation of the radiation beam within the treatment head
• CPC Class Codes: A61N 5/1048 Monitoring, verifying, controlling systems and methods
• CPC Class Codes: A61N 5/1049 for verifying the position of the patient with respect to the radiation beam
• CPC Class Codes: A61N 5/1064 for adjusting radiation treatment in response to monitoring
• CPC Class Codes: A61N 5/1067 in real time, i.e. during treatment

Abstract

Radiotherapy controlling, treatment sinograms may be directly modified to correct for real time motion of patients or portions of patients resulting from physiological or other activity. Precalculated partial sinograms representing treatments of portions of a patient may be assembled to obtain a treatment sinogram for the entire patient without delay from conventional planning software. The partial sinograms are modified as representations of their corresponding portions and manipulated to conform to the particular dimensions of an actual patient. This constructed sinogram may be used directly or as a starting point for iterative optimization.

Claims

1. A method of operating a radiation therapy machine providing a radiation beam of individually energy and/or fluence modulated radiation rays directed along a radiation beam axis, the radiation beam axis positionable at a range of angles about a patient, the method comprising the steps of:

(a) accepting a ray treatment sinogram of rows and columns providing energy and/or fluence of different rays for a given angle of the radiation beam axis, in rows, and energy and/or fluence of a given ray for different angles of the beam axis, in columns, for a patient at a first position;

(b) developing patient movement data indicating patient motion from the first position to a second position;

(c) for each given beam axis angle of the ray treatment sinogram shifting the corresponding row of the treatment sinogram according to a component of the patient motion perpendicular to the given beam axis and scaling the corresponding row of the ray treatment sinogram according to a component of the patient motion parallel to the given beam axis;

whereby divergence of the fan beam of treatment radiation may be accommodated.

2. The method of claim 1 wherein step (c) is performed by:

(i) rebinning the ray treatment sinogram into a parallel ray treatment sinogram providing equivalent treatment of the patient in the first position with a virtual radiation therapy machine having individually energy and/or fluence modulated radiation rays separated but mutually parallel along a divergence axis about a radiation beam axis;

(ii) for each given beam axis angle of the parallel ray treatment sinogram shifting the corresponding row of the treatment sinogram according to a component of the patient motion perpendicular to the given beam axis;

(iii) reverse rebinning the parallel ray treatment sinogram as modified by step (ii) back to a ray treatment sinogram.

3. The method of claim 1 wherein step (b) develops patient movement data by comparing tomographic images of the patient in the first and second positions.

4. The method of claim 1 wherein step (b) develops patient movement data by a patient movement model receiving as an input a physiological signal selected from the group consisting of:

a respiration signal and a heartbeat signal.

5. The method of claim 1 wherein the radiation therapy machine provides the individually energy and/or fluence modulated radiation rays by means of a multi-leaf collimator having fixed leaf separation and wherein step (c) further includes the step of resampling the modified rows of the diverging ray treatment sinogram to conform with the leaf reparation of the multi-leaf collimator.

6. The method of claim 1 wherein the patient motion is non-uniform such as caused by a change in shape of internal structure to the patient and wherein at step (c) the component of the patient motion perpendicular to the given beam axis and the resultant shifting are a function of position perpendicular to the given beam axis and the component of the patient motion parallel to the given beam axis and the resulting scaling are functions of position parallel to the given beam axis;

whereby expansion and contraction of internal organs may be accommodated.

9. The method of claim 1 wherein step (b)(i) develops patient movement data by a patient movement model receiving as an input a physiological signal selected from the group consisting of:

a respiration signal and a heartbeat signal.

10. The method of claim 9 wherein the modification of the treatment sinogram shifts corresponding rows of the treatment sinogram according to a component of the patient motion perpendicular to the given beam axis.

11. The method of claim 10 wherein the radiation therapy machine provides the individually energy and/or fluence modulated radiation rays by means of a multi-leaf collimator having fixed leaf separation and wherein the modification of the treatment sinogram further includes the step of resampling the modified rows of the treatment sinogram to conform with the leaf separation of the multi-leaf collimator.

12. The method of claim 9 wherein the change in patient position is non-uniform such as caused by a change in shape of internal structure to the patient and wherein the rows of the treatment sinogram are modified by a shifting that is a function of the position perpendicular to the given beam axis;

whereby change of shape of internal organs may be accommodated.

7. A method of operating a radiation therapy machine providing a radiation beam of individually energy and/or fluence modulated radiation rays directed generally along a beam axis and spaced apart perpendicular to the beam axis, the radiation beam axis positionable at a range of angles about a patient, the method comprising the steps of:

(a) accepting a treatment sinogram of rows and columns providing energy and/or fluence of different rays for a given angle of the radiation beam axis, in rows, and energy and/or fluence of a given ray for different angles of the beam axis, in columns, for a patient at a first position;

(b) during radiation treatment using the treatment sinogram;

(i) detecting patient movement data indicating patient motion from the first position to a second position;

(ii) directly modifying the treatment sinogram according to the detected patient motion;

(c) continuing the radiation treatment using the treatment sinogram as modified by step (b)(ii);

whereby rapid adjustments to the treatment plan may be effected.

8. The method of claim 7 wherein step (b)(i) develops patient movement data by comparing tomographic images of the patient in the first position with tomographic images of the patient in the second position taken during radiation therapy.

13. The method of claim 7 wherein step (b)(i) develops patient movement data through a motion sensor selected from the group consisting of:

a magnetic resonance imager;

an optical scanner, and a location fixture attached to the patient.

14. A method of operating a radiation therapy machine providing a radiation beam of individually energy modulated radiation rays directed generally along a beam axis and spaced apart perpendicular to the beam axis, the radiation beam axis positionable at a range of angles about a patient, the method comprising the steps of:

(a) preparing a library of partial sinograms of rows and columns, providing energy and/or fluence of different rays for a given angle of the radiation beam axis, in rows, and energy and/or fluence of a given ray for different angles of the beam axis, in columns, each partial sinogram corresponding to one of a variety of patient elements in first modes;

(b) arranging combinations of a set of representations of the patient elements to second modes so as to model a given patient requiring radiation treatment;

(c) determining for each of the patient elements of the set alteration data indicating changes in the patient elements between the first and second modes;

(d) modifying the partial sinograms of each of the patient elements of the set according to the alteration data; and

(e) combining the modified partial sinograms to provide a treatment sinogram of the patient.

15. The method of claim 14 wherein the alteration data indicates changes in location and dimension of the patient elements.

16. The method of claim 14 wherein in step (d) for each given beam axis angle of each partial sinogram, the corresponding row of the partial sinogram is shifted according to a component of the alteration of the patient element perpendicular to the given beam axis and the corresponding row of the partial sinogram is scaled according to a component of alteration of the patient element parallel to the given beam axis.

17. The method of claim 14 wherein prior to step (c) the arrangement of the patient elements is further modified by real-time data indicating motion of the patient.

18. The method of claim 14 wherein that patient elements are simple geometric regions.

19. The method of claim 14 wherein that patient elements are models of patient organs.

20. The method of claim 14 wherein the partial sinograms are arranged according to a dose map for the patient and including between steps (d) and (e) the step of optimizing the treatment sinogram to better conform with the dose map.