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.