Abstract: A radiotherapy apparatus adapted for use with a Magnetic Resonance Imaging (MRI) system, the radiotherapy apparatus comprising a linear accelerator, the linear accelerator including an electron source. In the linear accelerator electrons which are introduced by the source are accelerated to impact on a target and produce a beam of radiotherapeutic radiation. The linear accelerator has an accelerator waveguide within which the electrons are accelerated and an external waveguide enclosure; this enclosure extends substantially continuously over the accelerator waveguide.

Abstract: A radiotherapy apparatus adapted for use with a Magnetic Resonance Imaging (MRI) system, the radiotherapy apparatus comprising a linear accelerator, the linear accelerator including an electron source. In the linear accelerator electrons which are introduced by the source are accelerated to impact on a target and produce a beam of radiotherapeutic radiation. The linear accelerator has an accelerator waveguide within which the electrons are accelerated and an external waveguide enclosure; this enclosure extends substantially continuously over the accelerator waveguide.

Abstract: Apparatus for measuring radiation beam energy output from a radiation beam source, comprising a first beam energy sensor at a first distance from the radiation beam source along the radiation beam axis; a second beam energy sensor located at a second distance from the radiation beam source along the radiation beam axis; and an energy absorbing layer, for example a layer that removes a part of the low energy content of the beam or a layer that absorbs at least 1% of the beam energy, located between the first and second sensors, and positioned such that radiation passing through the first sensor also passes through the energy absorbing layer before entering the second sensor.

Abstract: A method of determining the shape of a radiation beam of a radiotherapy system at a treatment position, the system comprising a radiation source and a multi-leaf collimator disposed between the radiation source and the treatment position. The multi-leaf collimator includes an array of moveable leaves positioned to intersect and block parts of the radiation beam to define the shape of the radiation beam at the treatment position. The leaves of a group are aligned such that the planes of the leaves in that group converge at a point displaced laterally from the radiation source. The method includes, for each leaf in the array positioned to intersect the radiation beam, determining a projected width with respect to the radiation beam, the projected width being greater than the thickness of the respective leaf, and using the projected leaf width to determine the shape of the radiation beam at the treatment position.

Abstract: Apparatus for measuring radiation beam energy output from a radiation beam source, comprising a first beam energy sensor at a first distance from the radiation beam source along the radiation beam axis; a second beam energy sensor located at a second distance from the radiation beam source along the radiation beam axis; and an energy absorbing layer, for example a layer that removes a part of the low energy content of the beam or a layer that absorbs at least 1% of the beam energy, located between the first and second sensors, and positioned such that radiation passing through the first sensor also passes through the energy absorbing layer before entering the second sensor.

Abstract: A method of determining the shape of a radiation beam of a radiotherapy system at a treatment position, the system comprising a radiation source and a multi-leaf collimator disposed between the radiation source and the treatment position. The multi-leaf collimator includes an array of moveable leaves positioned to intersect and block parts of the radiation beam to define the shape of the radiation beam at the treatment position. The leaves of a group are aligned such that the planes of the leaves in that group converge at a point displaced laterally from the radiation source. The method includes, for each leaf in the array positioned to intersect the radiation beam, determining a projected width with respect to the radiation beam, the projected width being greater than the thickness of the respective leaf, and using the projected leaf width to determine the shape of the radiation beam at the treatment position.

Abstract: A method of aligning the radiation beam in a radiotherapy system comprising a source for producing a beam of radiation and an imaging device for imaging from the beam, both mounted to be rotatable about an axis, a fiducial phantom between the source and imaging device, the method comprising: rotating the beam and imaging device in a trajectory about the axis while obtaining images of the fiducial phantom from a plurality of different angles, at least one image including a feature of the imaging apparatus, adjusting the trajectory of the source relative to that feature to position the isocenter substantially in the center of the volume, determining from each image of the fiducial phantom the position of the source at the rotational position the image was obtained, and calculating the center of rotation of the positions of the source to define the isocenter of the system.

Abstract: A linear accelerator is disclosed, having a series of interconnected cavities through at least some of which an rf signal and an electron beam are sent, comprising at least one variable coupler projecting into the a cavity of the series, a control apparatus adapted to interpret an electrical signal from the coupler and derive diagnostic information as to the electron beam therefrom, wherein the control apparatus is further adapted to vary the interaction of the at least one coupler with the rf signal in dependence on the diagnostic information. Thus, the accelerator properties can be adjusted by encouraging or inciting an Higher-Order Mode (“HOM”) having a desired effect such as bunching and/or deflecting. The coupler could be rotateable, and partially or fully retractable, to allow its influence to be adjusted and/or for it to be removed from service when not needed.

Abstract: A method of aligning the radiation beam in a radiotherapy system comprising a source for producing a beam of radiation and an imaging device for imaging from the beam, both mounted so as to be rotatable about an axis using a fiducial phantom between the source and the imaging device, the method comprising: rotating the beam and imaging device in a trajectory about the axis while obtaining a plurality of images of the fiducial phantom from a plurality of different angles, wherein at least one image includes a feature of the imaging apparatus, adjusting the trajectory of the source relative to that feature so as to position the isocentre substantially centrally of the volume, determining from each image of the fiducial phantom the position of the source at the rotational position the image was obtained, and calculating the centre of rotation of the positions of the source to define the isocentre of the system.

Abstract: A linear accelerator is disclosed, having a series of interconnected cavities through at least some of which an rf signal and an electron beam are sent, comprising at least one variable coupler projecting into the a cavity of the series, a control apparatus adapted to interpret an electrical signal from the coupler and derive diagnostic information as to the electron beam therefrom, wherein the control apparatus is further adapted to vary the interaction of the at least one coupler with the rf signal in dependence on the diagnostic information. Thus, the accelerator properties can be adjusted by encouraging or inciting an Higher-Order Mode (“HOM”) having a desired effect such as bunching and/or deflecting. The coupler could be rotateable, and partially or fully retractable, to allow its influence to be adjusted and/or for it to be removed from service when not needed.