Radiotherapy device comprising a tilting mechanism

A method of tilting a source of radiation of a radiotherapy device, the radiotherapy device comprising a source of radiation and a drive member comprising one or more linear actuators configured to translate a plurality of carriages along a plurality of guide rails respectively to cause tilting of a support structure, wherein at least two of the plurality of guide rails are oblique with respect to one another, the method comprising:

• while the radiotherapy device is in a coplanar configuration, driving the one or more linear actuators to translate the carriages along the guide rails in a first direction to tilt the source of radiation into a non-coplanar configuration, and
• while the radiotherapy device is in the non-coplanar configuration, driving the linear actuators to translate the carriages along the guide rails in a second, opposite direction to thereby bring the source of radiation back to the coplanar configuration.