IMRT (Intensity Modulated Radiation Therapy) uses 3-D scans of the target area and surrounding tissue to guide the radiation beams to the tumor or the seroma (post-surgical site) from many different angles. At each of these angles, the intensity of the radiation is modulated and the shape changed to suit the shape of the target delivering a prescribed amount of radiation to each part of the target, and minimizing exposure to the surrounding healthy tissue. For breast cancer, radiation beams are projected at tangent angles in order to skim the chest wall, allowing for a maximum dose of radiation to be delivered to the target while minimizing exposure to the heart and lungs. For Varian Surgical Sciences.