Tangential fields. Improved reproducibility for breast-cancer treatment

The authors describe an isocentric technique to set up tangential fields for breast-cancer therapy. The setup parameters (source-to-surface distance measured at the midline of the sternum, lateral shift of the treatment couch, and the gantry angle) are predetermined from a computed-tomographic image and a transverse contour which is obtained under treatment-like conditions. This procedure does not require breast immobilization and does not rely on skin marks on the breast.