Incorporating multiple targets in trajectory optimization for radiotherapy treatment planning

Patent metadata

Field	Value
Publication number	US-10946216-B2
Application number	US-201816235205-A
Country	US
Kind code	B2
Filing date	Dec 28, 2018
Priority date	Dec 28, 2018
Publication date	Mar 16, 2021
Grant date	Mar 16, 2021

Abstract

Methods of treatment trajectory optimization for radiotherapy treatment of multiple targets include determining beam's eye view (BEV) regions and a BEV region connectivity manifold for each target group of a plurality of target groups separately. The information contained in the BEV regions and the BEV region connectivity manifolds for all target groups is used to guide an optimizer to find optimal treatment trajectories. To improve the visibility of insufficiently exposed voxels of planning target volumes (PTVs), a post-processing step may be performed to enlarge certain BEV regions, which are considered for exposing during treatment trajectory optimization.

First claim

What is claimed is:

1. A method of trajectory optimization for radiotherapy treatment of multiple targets, the method comprising:
providing a patient model including a plurality of planning target volumes (PTVs);
defining a delivery coordinate space (DCS) having a plurality of vertices, each respective vertex defining a respective beam's eye view (BEV) plane;
for each respective PTV of the plurality of PTVs:
for each respective BEV plane of a respective vertex:
for each respective pixel of the respective BEV plane:
evaluating a dose of the respective PTV from a respective beamlet originating from the respective vertex and passing through the respective pixel of the respective BEV plane; and
evaluating a respective BEV score of the respective pixel of the respective BEV plane for the respective PTV based at least in part on the dose of the respective PTV from the respective beamlet;

determining a PTV-specific threshold BEV score for the respective PTV based at least in part on the BEV scores of the pixels of the BEV planes for the respective PTV;
for each respective BEV plane of the respective vertex:
determining one or more respective BEV regions of the respective PTV by comparing each respective BEV score of the respective pixel for the respective PTV to the PTV-specific threshold BEV score, wherein pixels within the one or more respective BEV regions have BEV scores greater than or equal to the PTV-specific threshold BEV score; and

determining a respective BEV region connectivity manifold for the respective PTV representing connections between BEV regions of adjacent vertices; and

selecting one or more optimal treatment trajectories for irradiating the plurality of PTVs based on the BEV region connectivity manifolds for the plurality of PTVs.

2. The method of claim 1 , wherein the one or more optimal treatment trajectories comprise one or more VMAT arcs.

3. The method of claim 1 , wherein each vertex in the DCS comprises an isocenter, a gantry angle, and a couch angle.

4. The method of claim 1 , wherein selecting the one or more optimal treatment trajectories comprises performing a stateful graph optimization.

5. The method of claim 4 , wherein the stateful graph optimization is performed on a graph defined by a plurality of nodes, each node associated with a respective vertex in the DCS and a state relating to a set of PTV angular fluxes for a set of sampling points distributed among the plurality of PTVs, each PTV angular flux relating to novelty of directional vectors of incident beamlets through a closed surface centered at a respective sampling point of the set of sampling points.

6. The method of claim 5 , wherein the closed surface comprises a quadrilateralized spherical cube.

7. The method of claim 5 , wherein the set of sampling points is distributed among the plurality of PTVs according to weighting factors associated with the plurality of PTVs.

8. The method of claim 5 , wherein the set of sampling points is distributed among the plurality of PTVs such that a point density for each respective PTV is a decreasing function of a volume of the respective PTV.

9. The method of claim 4 , wherein selecting the one or more optimal treatment trajectories comprises:
selecting a plurality of candidate trajectories that minimize a min-distance function based on the BEV region connectivity manifolds for the plurality of PTVs; and
selecting the one or more optimal treatment trajectories among the plurality of candidate trajectories that maximize a max-distance function.

10. The method of claim 9 , further comprising:
for each respective PTV of the plurality of PTVs:
for each respective BEV plane of a respective vertex:
determining a region score for each respective pixel of the respective BEV plane based on the respective BEV score of the respective pixel; and
determining an average region score for each respective BEV region of the one or more BEV regions based on the region scores of the pixels of the respective BEV region;

wherein the min-distance function is inversely proportional to the average region score of each respective BEV region for each respective PTV, and the max-distance function is proportional to the average region score of each respective BEV region for the respective PTV.

11. The method of claim 10 , wherein the region score for each respective pixel has a normalized positive value if the respective pixel is within one of the one or more BEV regions, and a negative value if the respective pixel is not within any of the one or more BEV regions.

12. The method of claim 10 , wherein the average region score of each respective BEV region for each respective PTV is given a respective weight associated with the respective PTV.

13. The method of claim 10 , further comprising:
for each respective BEV plane of a respective vertex for a subset of the plurality of vertices of the DCS:
collapsing a first BEV region of a first PTV of the plurality of PTVs and a second BEV region of a second PTV of the plurality of PTVs into a single BEV region.

14. The method of claim 1 , wherein the patient model further includes an organ at risk (OAR), the method further comprising:
for each respective BEV plane of a respective vertex:
for each respective pixel of the respective BEV plane:
evaluating a dose of the OAR from a respective beamlet originating from the respective vertex and passing through the respective pixel of the respective BEV plane;

wherein evaluating the respective BEV score of the respective pixel of the respective BEV plane for the respective PTV comprises evaluating a weighted combination of the dose of the respective PTV and the dose of the OAR from the respective beamlet.

15. The method of claim 14 , wherein the dose of the respective PTV is assigned a positive weight, and the dose of the OAR is assigned a negative weight.

16. The method of claim 1 , wherein the plurality of PTVs includes a first PTV and a second PTV that fully or partially overlap with each other spatially.

17. The method of claim 1 , wherein the plurality of PTVs includes a first PTV and a second PTV that are spatially disjoint with each other.

18. A method of trajectory optimization for radiotherapy treatment, the method comprising:
providing a patient model including one or more planning target volumes (PTVs), the one or more PTVs including a first PTV;
defining a delivery coordinate space (DCS) having a plurality of vertices, each respective vertex defining a respective beam's eye view (BEV) plane;
for each respective BEV plane of a respective vertex:
for each respective pixel of the respective BEV plane:
evaluating a dose of the first PTV from a respective beamlet originating from the respective vertex and passing through the respective pixel of the respective BEV plane; and
evaluating a respective BEV score of the respective pixel of the respective BEV plane based at least in part on the dose of the first PTV from the respective beamlet;

determining a global threshold BEV score for the first PTV based on the BEV scores of the pixels of the BEV planes;
for each respective BEV plane of the respective vertex:
determining one or more initial BEV regions by comparing the respective BEV score of each respective pixel to the global threshold BEV score, wherein pixels within the one or more initial BEV regions have BEV scores greater than or equal to the global threshold BEV score, and each respective initial BEV region exposes one or more voxels of the first PTV to beamlets corresponding to the respective vertex;
for each

Assignees

• Varian Medical Systems Int Ag
• The Board Of Trustees Of The Leland Stanford Junior Univ Office Of The General Counsel

Inventors

• Locke Christopher Barry
• Ollila Santtu
• Bush Karl Kenneth

Classifications

• A61N2005/1097

  Means for immobilizing the patient · CPC title

• A61N2005/1092

  Details · CPC title

• A61N5/1077

  Beam delivery systems · CPC title

• A61N5/1047

  with movement of the radiation head during application of radiation, e.g. for intensity modulated arc therapy or IMAT · CPC title

• A61N5/1031 Primary

  using a specific method of dose optimization · CPC title