Preparation for radiotherapy: modelling of a patient's face in the initial stages of making a plastic face mask, used to immobilise the head during treatment sessions. The finished mask is made from a cast of the white imprint (right). Modern radiotherapy endeavours to deliver a radiation dose that is sufficient to destroy a tumour, yet cause minimal damage to surrounding healthy tissue. This is achieved by aiming a beam of limited radiation dosage from different directions during a number of sessions, so that the target receives a cumulative, effective dose. CT scans & computer simulations are employed in planning such treatment regimes.