CT scanning: its value in the planning of radiotherapy of the chest wall.

The thickness of the chest wall varies considerably, but measurement of this parameter is essential for the planning of adequate irradiation without damaging an excessive volume of lung tissue. The radiation dose distribution was checked in 55 patients, using data from the CT-scanner. Although the treatment volume as changed in only one patient, significant inaccuracies in dose distribution were exposed in 15 patients, especially in the internal mammary lymph node regions, which were often underdosed. If the patients were to have been treated with electron fields then the dosage inadequacies would have been even more dramatic.