For the delivery of high precision radiation treatment, the accuracy with which a target is irradiated at individual gantry, collimator and patient couch orientation is traditionally verified in 2D. With the QA device described herein, the coverage of the gantry is uniquely measured in 3D. The method of the present invention, combining with the collimator and patient couch measurements, allows the reconstruction of the target coverage in full 3D, which was not possible before. In addition, the method of the present invention can be applied to decompose the traditional quality assurance measurements of combined gantry, collimator and patient couch orientations with standard devices. Such an application provides a comprehensive description of the irradiation accuracy.
