Determining a distribution of spots of varying sizes for ion beam therapy using optimization

Patent metadata

Field	Value
Publication number	US-11020616-B2
Application number	US-201816625871-A
Country	US
Kind code	B2
Filing date	Jun 26, 2018
Priority date	Jun 28, 2017
Publication date	Jun 1, 2021
Grant date	Jun 1, 2021

Abstract

According to a first aspect, it is presented a method for determining a treatment plan comprising a distribution of spots for use with ion beam therapy for providing the spots in a target volume. The method comprises the steps of: selecting energy layers to be used in the treatment plan; determining a number of spot sizes to use; generating, for each energy layer, one copy of the energy layer for each spot size to use and populating each copy with spots of the spot size for that copy; optimizing spots of all copies of all energy layers, by repeatedly varying a weight of at least a subset of the spots and calculating an effect on a performance measurement, wherein the performance measurement is calculated by combining a plurality of evaluation criteria, comprising a first criterion related to total treatment time and a second criterion related to a desired dose distribution.

First claim

The invention claimed is:

1. A method for determining a treatment plan comprising a distribution of spots of varying sizes for use with ion beam therapy for providing the spots in a target volume, wherein each spot represents a collection of ions of a specific energy and of a specific spot size at a specific lateral location, the method being performed in a treatment planning system and comprising the steps of:
selecting energy layers to be used in the treatment plan;
determining a number, greater than one, of spot sizes to use;
generating, for each energy layer, one copy of the energy layer for each spot size to use, and populating each copy with spots of the spot size for that copy; and
optimizing spots of all copies of all energy layers, by repeatedly varying a weight, related to the number of ions that are delivered to the spot, of at least a subset of the spots and calculating an effect on a performance measurement, until variations of the weights fail to improve the performance measurement more than a threshold amount, wherein the performance measurement is calculated by combining a plurality of evaluation criteria, wherein the plurality of evaluation criteria comprises a first criterion which improves the performance measurement when a total treatment time is reduced and a second criterion which improves the performance measurement when a desired dose distribution in the treatment volume is achieved,
wherein the second criterion improves the performance measurement when a penumbra outside the target volume is reduced, and
wherein the treatment plan is provided to an apparatus configured to apply the treatment plan to a patient.

2. The method according to claim 1 , wherein the step of optimizing comprises performing a spot filtering to remove spots with weights below a threshold value.

3. The method according to claim 1 , further comprising the step, after the step of optimizing spots, of:
finding any multi spot size region of a single energy layer which is covered by spots of different sizes of respective copies of the energy layer;
determining, in each multi spot size region, Which single spot size to keep and removing the spots of other spot sizes in the multi spot size region; and
returning to the step of optimizing spots.

4. The method according to claim 3 , further comprising the step, after the step of determining which spot size to keep, of:
adding, in each multi spot size region when the spot size to keep is not the largest spot size in the multi spot size region, spots of the spot size to keep, to improve coverage.

5. The method according to claim 3 , wherein the step of determining which spot size to keep comprises determining to keep a spot size according to a user parameter.

6. A treatment planning system for determining a treatment plan comprising a distribution of spots of varying sizes for use with ion beam therapy for providing the spots in a target volume, wherein each spot represents a collection of ions of a specific energy level and of a specific spot size at a specific lateral location, the treatment planning system comprising:
a processor; and
a memory storing instructions that, when executed by the processor, cause the treatment planning system to:
select energy layers to be used in the treatment plan;
determine a number, greater than one, of spot sizes to use;
generate, for each energy layer, one copy of the energy layer for each spot size to use and populating each copy with spots of the spot size for that copy; and
optimize spots of all copies of all energy layers, by repeatedly varying a weight, related to the number of ions that are delivered to the spot, of at least a subset of the spots and calculating an effect on a performance measurement, until variations of the weights fail to improve the performance measurement more than a threshold amount, wherein the performance measurement is calculated by combining a plurality of evaluation criteria, wherein the plurality of evaluation criteria comprises a first criterion which improves the performance measurement when a total treatment time is reduced and a second criterion which improves the performance measurement when a desired dose distribution in the treatment volume is achieved,
wherein the second criterion improves the performance measurement when a penumbra outside the target volume is reduced, and
wherein the treatment plan is provided to an apparatus configured to apply the treatment plan to a patient.

7. The treatment planning system according to claim 6 , further comprising instructions that, when executed by the processor, cause the treatment planning system to:
find any multi spot size region of a single energy layer which is covered by spots of different sizes of respective copies of the energy layer;
determine, in each multi spot size region, which single spot size to keep and removing the spots of other spot sizes in the multi spot size region; and
return to the instructions to optimize spots.

8. The treatment planning system according to claim 7 , further comprising instructions that, when executed by the processor, cause the treatment planning system to:
add, in each multi spot size region when the spot size to keep is not the largest spot size in the multi spot size region, spots of the spot size to keep, to improve coverage.

9. The treatment planning system according to claim 7 , wherein the instructions to determine, which spot size to keep comprise instructions that, when executed by the processor, cause the treatment planning system to determine to keep a spot size according to a user parameter.

10. A treatment planning system for determining a treatment plan comprising a distribution of spots of varying sizes for use with ion beam therapy for providing the spots in a target volume, wherein each spot represents a collection of ions of a specific energy level and of a specific spot size at a specific lateral location, the treatment planning system comprising:
means for selecting energy layers to be used in the treatment plan;
means for determining a number, greater than one, of spot sizes to use;
means for generating, for each energy layer, one copy of the energy layer for each spot size to use and populating each copy with spots of the spot size for that copy; and
means for optimizing spots of all copies of all energy layers, by repeatedly varying a weight, related to the number of ions that are delivered to the spot, of at least a subset of the spots and calculating an effect on a performance measurement, until variations of the weights fail to improve the performance measurement more than a threshold amount, wherein the performance measurement is calculated by combining a plurality of evaluation criteria, wherein the plurality of evaluation criteria comprises a first criterion which improves the performance measurement when a total treatment time is reduced and a second criterion which improves the performance measurement when a desired dose distribution in the treatment volume is achieved,
wherein the second criterion improves the performance measurement when a penumbra outside the target volume is reduced, and
wherein the treatment plan is provided to an apparatus configured to apply the treatment plan to a patient.

11. A non-transitory computer readable medium having a computer program that when executed on a computer causes the computer to perform the method of claim 1 .

Assignees

• Raysearch Lab Ab

Inventors

• Engwall Erik
• Glimelius Lars
• Janson Martin

Classifications

• A61N5/1031 Primary

  using a specific method of dose optimization · CPC title

• A61N2005/1087

  Ions; Protons · CPC title

• A61N5/103 Primary

  Treatment planning systems · CPC title

• A61N5/1043

  Scanning the radiation beam, e.g. spot scanning or raster scanning · CPC title