Dose-distribution conventional breast beams relative to CT-based breast target volumes. Representation of 95%-isodose (green) resulting from conventional breast beams and computed tomography (CT)-based clinical target volume (CTV) and planning target volume (PTV). Note the areas of PTV (red) not covered by 95%-isodose when conventional beams are used. Under-dosage of PTV is caused by including additional tissue (marked yellow-wash areas) into the CTV.