The daily reproducibility of large, complex-shaped radiotherapy fields to the thorax and neck.
A series of patients treated with complex fields to the thorax and neck utilising individually tailored shielding blocks made from low-melting-point alloy (LMPA), were investigated using treatment verification film to identify field placement errors. A total of 19 patients yielded 171 machine verification films, which were analysed. It was found that on 21% of occasions the intended treatment volume was partially shielded, by more than 1 cm, by the lead blocks prescribed to protect the lungs. On half of these occasions (11% of the total), the areas erroneously shielded contained known disease. Suggestions are made for minimising such errors in the future.
D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D006689:Hodgkin Disease / Q000532:radiotherapy; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D008482:Mediastinum / Q000000981:diagnostic imaging; D011835:Radiation Protection; D011859:Radiography; D013899:Thoracic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*