Devices and methods for delivering non-coplanar radiotherapy

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.

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.