Radiation treatment methods for breast cancer following resection, both intraoperative and post operative, involve mapping preferably using an electronic x-ray source, and can include rotation of a direction source. By using a very rapid, near-instantaneous method of pathology of tissue margins following resection, the invention carries out intraoperative radiation treatment, preferably with the patient remaining anesthetized. Whether or not radiation is intraoperative, the invention preferably includes a mapping procedure using an electronic source that is progressed through the resection cavity while radiation dose is sensed at one or more points, to determine the shape of the resection cavity.