MODEL RELEASED. Gamma knife radiotherapy. Head frame being removed after gamma knife radiotherapy. This is usually used to treat brain tumours. The frame prevents movement of the head during treatment. The patient receives a gamma radiation dose distributed through the ports of a collimator helmet. It is targeted at a specific region of the brain and has a minimal effect on surrounding tissue, since each beam is of a low dose. The therapy provides access to areas of the brain that cannot otherwise be reached. Photographed at the Gamma Knife Centre, Erasme Hospital, Brussels, Belgium.