Abstract: A water tank apparatus for use with a radiotherapy system, comprising a base, side walls, end walls, and a top wall, together defining a tank structure, wherein an aperture is defined in the top wall near one end wall, and an upstanding rim surrounding the aperture; and a sensor mounting body fixed within the tank structure, and having formations by which a radiation sensor can be located in a fixed position within the tank structure so as to detect radiation at a point equidistant from the side wall and top wall and base.

Abstract: A water tank apparatus for use with a radiotherapy system, comprising a base, side walls, end walls, and a top wall, together defining a tank structure, wherein an aperture is defined in the top wall near one end wall, and an upstanding rim surrounding the aperture; and a sensor mounting body fixed within the tank structure, and having formations by which a radiation sensor can be located in a fixed position within the tank structure so as to detect radiation at a point equidistant from the side wall and top wall and base.

Abstract: A method for measurement of dose distribution in a radiotherapy apparatus includes providing a detector holder situated at least partially within a tank, the detector holder comprising a radio-opaque marker and a visual reference point, the marker and the reference point being separated and in a fixed spatial relationship to each other; locating the tank within a bore of the radiotherapy apparatus; rotating a gantry and monitoring the position of the detector holder with an imaging apparatus; vertically displacing the detector holder until the reference point is positioned at a desired level, and adding liquid to or removing liquid from the tank until the surface of the liquid is level with the reference point. Features of the detector holder and tank are also described.

Abstract: A method for measurement of dose distribution in a radiotherapy apparatus includes providing a detector holder situated at least partially within a tank, the detector holder comprising a radio-opaque marker and a visual reference point, the marker and the reference point being separated and in a fixed spatial relationship to each other; locating the tank within a bore of the radiotherapy apparatus; rotating a gantry and monitoring the position of the detector holder with an imaging apparatus; vertically displacing the detector holder until the reference point is positioned at a desired level, and adding liquid to or removing liquid from the tank until the surface of the liquid is level with the reference point. Features of the detector holder and tank are also described.