Devices and methods for delivering non-coplanar radiotherapy

1 . A radiotherapy apparatus comprising:

a radiation source;

a beam shaping apparatus;

a rotatable gantry configured to rotate about a rotation axis;

a beam receiving apparatus; and

a controller configured to control the beam shaping apparatus, wherein:

the radiation source is configured to deliver radiation in each of a coplanar configuration and at least one non-coplanar, tilted, configuration;

in the coplanar configuration, the radiation source is positioned to rotate about the rotation axis and to rotate in a first plane;

in the at least one non-coplanar, tilted, configuration, the radiation source is non-coplanar with respect to the first plane such that a field of radiation produced by the radiation source is directed at an oblique angle relative to the first plane and the rotation axis;

in the at least one non-coplanar, tilted, configuration, the radiation source is positioned to rotate in a respective second plane parallel to and displaced from the first plane;

the beam receiving apparatus remains in the same place relative to the rotatable gantry when the radiation source is in the coplanar configuration or the at least one non-coplanar, tilted, configuration;

the beam shaping apparatus is configured to direct the radiation produced by the radiation source towards the beam receiving apparatus in each of the coplanar configuration and the at least one non-coplanar, tilted, configuration; and

the controller is configured to:

control the beam shaping apparatus to apply a limit on the field of radiation produced by the radiation source based on whether the radiation source is configured in the coplanar configuration or the at least one non-coplanar, tilted, configuration;

apply the limit when the radiation source is in the at least one non-coplanar, tilted, configuration to prevent the field of radiation from extending beyond the beam receiving apparatus; and

remove the limit when the radiation source is in the coplanar configuration.

2 . The radiotherapy apparatus of claim 1 , wherein the beam receiving apparatus comprises at least one of a beam stopper or a radiation detector.

3 . The radiotherapy apparatus of claim 2 , wherein the controller is further configured to:

determine a spread of the radiation field using one or more signals from the radiation detector; and

control the beam shaping apparatus to reduce the spread of the field when the determined spread of the radiation field is within a threshold distance from an edge of the radiation detector.

4 . The radiotherapy apparatus of claim 1 , wherein the controller is configured to:

control the beam shaping apparatus such that all of the radiation in the field of radiation is incident on the beam receiving apparatus.

5 . The radiotherapy apparatus of claim 1 , wherein, in the at least one non-coplanar, tilted, configuration, the controller is configured to follow an operational rule defining a limit of retraction of at least one beam shaping member of the beam shaping apparatus.

6 . The radiotherapy apparatus of claim 5 , wherein application of the operational rule is dependent on whether the radiation source is in the coplanar configuration or the at least one non-coplanar, tilted, configuration.

7 . The radiotherapy apparatus of claim 5 , wherein the at least one beam shaping member is at least one of a diaphragm or a leaf of a multi-leaf collimator (MLC).

8 . The radiotherapy apparatus of claim 5 , wherein the beam shaping apparatus is a multi-leaf collimator (MLC) and the limit is applied such that, in the at least one non-coplanar, tilted, configuration, one leaf, or a plurality of adjacent leaves, of the MLC have a limit of retraction such that the one leaf or the plurality of adjacent leaves does not retract from a maximum extension into the radiation field.

9 . The radiotherapy apparatus of claim 1 , wherein the controller is further configured to:

control the radiation source.

10 . The radiotherapy apparatus of claim 1 , wherein the controller is configured to:

control the beam shaping apparatus to adjust an angle of the field of radiation relative to a rotation axis.

11 . The radiotherapy apparatus of claim 1 , wherein the radiation source and beam receiving apparatus are mounted on opposite sides of the rotatable gantry.

12 . The radiotherapy apparatus of claim 1 , wherein, in the at least one non-coplanar, tilted, configuration, the radiation source is configured to direct the field of radiation at an oblique angle relative to the rotation axis.

13 . The radiotherapy apparatus of claim 12 , wherein the controller is configured to:

control the beam shaping apparatus to modify the oblique angle of the field of radiation relative to the rotation axis when the radiation source is in the at least one non-coplanar, tilted, configuration.

14 . A method of controlling a field of radiation produced by a radiation source of a radiotherapy apparatus comprising a rotatable gantry configured to rotate about a rotation axis and a beam receiving apparatus, the method comprising:

switching the radiation source between a coplanar configuration and a non-coplanar configuration, wherein, in the coplanar configuration, the radiation source is positioned to rotate about the rotation axis and to rotate in a first plane, and wherein, in the non-coplanar configuration, the radiation source is non-coplanar with respect to the first plane such that the field of radiation produced by the radiation source is directed at an oblique angle relative to the first plane and the rotation axis, and wherein, in the non-coplanar configuration, the radiation source is positioned to rotate in a respective second plane parallel to and displaced from the first plane, and wherein the beam receiving apparatus remains in the same place relative to the rotatable gantry when the radiation source is in the coplanar configuration or the non-coplanar configuration;

applying a limit to the field of radiation produced by the radiation source based on whether the radiation source is configured in the coplanar configuration or the non-coplanar configuration, wherein the limit is applied to the field of radiation such that the radiation produced by the radiation source is directed towards the beam receiving apparatus in each of the coplanar configuration and at least one non-coplanar, tilted, configuration;

applying the limit when the radiation source is in the non-coplanar configuration to prevent the field of radiation from extending beyond the beam receiving apparatus; and

removing the limit when the radiation source is in the coplanar configuration.

15 . The method of claim 14 , wherein the field of radiation is limited such that all of the radiation in the field of radiation is incident on the beam receiving apparatus.

16 . The method of claim 14 , wherein the field of radiation is controlled by applying an operational rule defining a limit of retraction of at least one beam shaping member of a beam shaping apparatus.

17 . The method of claim 16 , wherein application of the operational rule is dependent on whether the radiation source is in the coplanar configuration or the non-coplanar configuration.

18 . The method of claim 16 , wherein the beam shaping apparatus is a multi-leaf collimator (MLC), and wherein the limit is applied such that, in the non-coplanar configuration, one leaf, or a plurality of adjacent leaves, of the MLC have a limit of retraction such that the one leaf or the plurality of adjacent leaves do not retract from a maximum extension into the radiation field.

19 . A non-transitory computer-readable medium comprising instructions that, when executed by one or more processors of a radiotherapy apparatus comprising a rotatable gantry configured to rotate about a rotation axis and a beam receiving apparatus, cause the one or more processors to:

switch a radiation source between a coplanar configuration and a non-coplanar configuration, wherein, in the coplanar configuration, the radiation source is positioned to rotate about the rotation axis and to rotate in a first plane, and wherein, in the non-coplanar configuration, the radiation source is non-coplanar with respect to the first plane such that a field of radiation produced by the radiation source is directed at an oblique angle relative to the first plane and the rotation axis, and wherein, in the non-coplanar configuration, the radiation source is positioned to rotate in a respective second plane parallel to and displaced from the first plane, and wherein the beam receiving apparatus remains in the same place relative to the rotatable gantry when the radiation source is in the coplanar configuration or the non-coplanar configuration;

apply a limit to the field of radiation produced by the radiation source based on whether the radiation source is configured in the coplanar configuration or the non-coplanar configuration, wherein the limit is applied to the field of radiation such that the radiation produced by the radiation source is directed towards the beam receiving apparatus in each of the coplanar configuration and at least one non-coplanar, tilted, configuration;

apply the limit when the radiation source is in the non-coplanar configuration to prevent the field of radiation from extending beyond the beam receiving apparatus; and

remove the limit when the radiation source is in the coplanar configuration.