A Technique for the Irradiation of the Upper Oesophagus in Megavoltage Therapy

In the treatment of patients with carcinoma of the oesophagus by the 8 MeV linear accelerator, a vertical cylinder of tissue extending from the most anterior to the most posterior limit of the tumour has been irradiated. To cover this volume three fields have been used, one anterior and two posterior. This arrangement has proved satisfactory for lesions of the middle and lower thirds of the oesophagus, but for lesions of the upper third, because of the curvature of the structure, a large volume of tissue, including the spinal cord, has been unnecessarily irradiated (Fig. 1). A technique has now been devised to restrict the radiation more closely to the upper third of the oesophagus. It will be seen from Fig. 1 that the upper oesophagus occupies an oblique position in the sagittal plane and a tumour dose has to be given to a volume lying obliquely in the lower neck and upper thorax. The tumour can be irradiated by two fields, each with a wedge filter, applied to the lower neck and front of chest, as shown in Fig. 2. The lower limit of the volume to be irradiated lies more posteriorly than the upper limit, so that a greater separation of the fields is required inferiorly. As a result the dose distribution along the length of the lesion would not be uniform—a higher dose being received at the upper end where the oesophagus lies nearer the skin.