High Quality Content by WIKIPEDIA articles! IntraOperative Electron Radiation Therapy (or "IOERT") is the application of electron radiation directly to the residual tumor or tumor bed during cancer surgery. . Electron beams are useful for intraoperative radiation treating because, depending on the electron energy, the dose falls off rapidly below the target site, therefore sparing underlying healthy tissue. IOERT has been called "precision radiotherapy", as the physician has direct visualization of the tumor, can exclude normal tissue from the field, and can also protect critical structures within the field and underlying the target volume. IOERT can be given at the time of surgery when microscopic residual tumor cells are most vulnerable to destruction. IOERT has been used in combination with EBRT as it results in less integral doses and shorter treatment times.