Methods for real-time image guided radiation therapy

Patent metadata

Field	Value
Publication number	US-10688320-B2
Application number	US-201815993325-A
Country	US
Kind code	B2
Filing date	May 30, 2018
Priority date	May 30, 2017
Publication date	Jun 23, 2020
Grant date	Jun 23, 2020

Abstract

Disclosed herein are systems and methods for guiding the delivery of therapeutic radiation using incomplete or partial images acquired during a treatment session. A partial image does not have enough information to determine the location of a target region due to, for example, poor or low contrast and/or low SNR. The radiation fluence calculation methods described herein do not require knowledge or calculation of the target location, and yet may help to provide real-time image guided radiation therapy using arbitrarily low SNR images.

First claim

The invention claimed is:

1. A method for delivering a radiation fluence comprising:
acquiring a partial image x i of a target region;
calculating a radiation fluence to be delivered to the target region by multiplying a radiation-firing matrix P and the partial image x i , wherein the radiation-firing matrix P is calculated based on a previously-acquired image X of the target region; and
delivering the calculated radiation fluence to the target region with a therapeutic radiation source.

2. The method of claim 1 , wherein the radiation-firing matrix P is a diagonal matrix of scalars s diag(s), such that P·x i =s⊙x i , where ⊙ is a point-wise product operation.

3. The method of claim 1 , wherein calculating the radiation fluence comprises convolving the radiation-firing matrix P with the partial image x i .

4. The method of claim 1 , wherein the radiation-firing matrix P is a Toeplitz matrix toep(f), such that P·x i =f*x i , where * is a convolution operation and f is a fluence to be delivered to the target region according to a treatment plan.

5. The method of claim 1 , wherein a signal-to-noise ratio (SNR) of the partial image x i is less than the SNR of the image X.

6. The method of claim 1 , wherein the partial image x i is acquired using a tomographic imaging system.

7. The method of claim 1 , wherein the partial image x i comprises a reconstruction from a set of positron annihilation emission paths, X-ray projections, or sub-samples in k-space from a MRI imaging pulse sequence.

8. The method of claim 1 , wherein the image X is a motion de-blurred image.

9. The method of claim 1 , further comprising:
selecting a projection angle α;
calculating a projected fluence f α of the calculated fluence at a radiation beam firing angle α and storing the projected fluence f α in a controller memory.

10. The method of claim 9 , wherein the therapeutic radiation source is in a radiation therapy system, and wherein delivering the calculated radiation fluence comprises:
moving the therapeutic radiation source to the radiation beam firing angle α, the radiation therapy system further comprising a multi-leaf collimator having an array of leaves disposed in a beam path of the therapeutic radiation source;
segmenting the projected fluence f α to collimator leaf position instructions and storing the leaf position instructions in controller memory;
adjusting the position of each of the collimator leaves according to the collimator leaf position instructions; and
emitting a radiation beam from the therapeutic radiation source.

11. The method of claim 10 , further comprising continuously repeating the projected fluence f α calculation and delivering radiation to the target region after each fluence calculation, until a desired fluence is applied.

12. The method of claim 11 , wherein calculating the projected fluence f α comprises:
selecting a projection angle α;
calculating a projection x i,α of the partial image x i at the radiation beam firing angle α and storing the projected partial image x i,α in controller memory; and
multiplying a per-angle radiation-firing matrix P α with the projected partial image x i,α (P α x i,α ), wherein the per-angle radiation-firing matrix P α comprises a set of radiation-firing matrices P i,α for each projection angle α.

13. The method of claim 12 , wherein the per-angle radiation-firing matrix P α is a Toeplitz matrix toep(p α ) that implements a convolution operation P α *x i .

14. The method of claim 12 , wherein the per-angle radiation-firing matrix P α is a diagonal matrix diag(p α ) that implements a pointwise multiplication operation p α ·x i .

15. The method of claim 12 , wherein the partial image x i is generated from a set of positron annihilation emission paths, X-ray projections, or sub-samples in k-space from a MRI imaging pulse sequence.

16. The method of claim 12 , wherein the signal-to-noise ratio (SNR) of the partial image x i is less than the SNR of the image X.

17. The method of claim 12 , wherein multiplying the radiation-firing matrix P and the partial image x i , selecting the projection angle α, calculating the projected fluence f α , moving the therapeutic radiation source, segmenting the projected fluence f α to collimator leaf position instructions, adjusting the position of each of the collimator leaves, and emitting the radiation beam occur within a specified time period after acquiring the partial image x i .

18. The method of claim 17 , wherein the specified time period is less than about 10 seconds.

19. The method of claim 18 , wherein the specified time period is less than about 5 seconds.

20. The method of claim 19 , wherein the specified time period is less than about 1 second.

21. The method of claim 10 , wherein the therapeutic radiation source is mounted on a rotatable gantry configured to rotate at a speed of about 20 RPM or more.

22. The method of claim 1 , further comprising applying a linear contrast filter to the partial image x i .

23. The method of claim 22 , wherein any negative values of the filtered partial image x i are added to a subsequent filtered partial image x i+1 .

24. The method of claim 1 , further comprising calculating a real-time delivered dose estimate.

25. The method of claim 1 , further comprising applying a spatial filter to the partial image x.

26. The method of claim 1 , wherein the previously-acquired image X is a first image and A is a known dose calculation matrix, and the method further comprises calculating an updated radiation-firing matrix P prescan by acquiring a second image X prescan and iterating through matrix values for P prescan such that the following conditions are met:
A·P·X≈A·P prescan ·X prescan.

27. The method of claim 26 , further comprising calculating a dose matrix D prescan based on X prescan , calculating a difference value between D prescan with a dose matrix D that has been calculated based on image X, and if the difference value exceeds a pre-selected threshold, generating a notification that the pre-selected threshold has been exceeded.

28. The method of claim 17 , wherein the specified time interval is about an hour.

29. The method of claim 1 , further comprising preprocessing a plurality of partial images x i with a transform T, wherein the image X is a sum of the preprocessed plurality of partial images x i :
X=ΣT ( x i ).

30. The method of claim 29 , wherein the transform T is a linear transform.

31. The method of claim 29 , wherein the transform T is a non-linear transform.

Assignees

• Reflexion Medical Inc

Inventors

• Voronenko Yevgen
• Olcott Peter Demetri
• Pal Debashish
• Bassalow Rostem

Classifications

• A61N2005/1074

  Details of the control system, e.g. user interfaces · CPC title

• A61N2005/1061

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

• A61N2005/1055

  using magnetic resonance imaging [MRI] · CPC title

• A61N2005/1052

  using positron emission tomography [PET] single photon emission computer tomography [SPECT] imaging · CPC title

• A61N5/1075

  for testing, calibrating, or quality assurance of the radiation treatment apparatus · CPC title