The value of computed tomography in planning radiotherapy of intra-thoracic tumours

The effectiveness of CT-scanning in radiotherapy planning is evaluated in 63 patients with intrathoracic tumours (59 bronchial, 4 oesophageal). The tumour target volumes are localized both by conventional techniques and with CT-scanning under conditions simulating the radiotherapy. The isodose distributions are calculated for both the conventional and CT-assisted approaches. The technique allows clearer demonstration of the loco-regional disease and exposes undesirable inhomogeneities of radiation dose. CT-scanning is found to be valuable in radiotherapy planning in 84% of the treatment series (field geometry: 54%; dosimetry: 52%).