ELIOT
Electron-beam intraoperative radiation therapy
This procedure is performed using a mobile linear accelerator that delivers an electron beam radiation with nominal energies between 3 and 12 MeV. The accelerator can be installed directly in the operating room using standard mobile screens of lead for radiation protection. The appropriate dose of radiation depends on the depth and thickness of the target volume to be treated. It is of primary importance to direct properly the electron beam. To achieve this, cylindrical applicators made of polymethyl methacrylate (Perspex) of different diameter and angles are used which can be adapted to the geometry of the tumor bed. During Nipple Sparing mastectomy, the effectiveness of a dose of 16 Gy delivered in a single fraction for irradiation of the residual parenchyma below the nipple-areola complex has been proven. After the removal of the gland, two metal discs with a diameter of approximately the size of the radiation field are placed below the residual areolar glandular area. The first disk, 5 mm thick made of lead, is placed in contact with the chest wall in order to shield the underlying structures. Above this, a 4 mm thick disk made of aluminium is placed which absorbs the electron radiation released back from the lead disk.
Reversing instead the position of protected discs, a significant contribution to the depth dose can be obtained by backscattering, such as to bring the dose obtained at 10 MeV to that obtained with a 12 MeV accelerator. This may be an additional reason to limit the choice of 10 MeV energy range. A layer of glandular tissue is left beneath the NAC to avoid necrosis and the sterile collimator of the linear accelerator is placed in contact with the nipple-areola complex with safety margins. Sterile gauzes soaked in saline are placed around the areola whit a hole present at the center of the gauze to leave the nipple free. This technical feature allows the operator to deliver the radiation dose in a more homogeneous way, avoiding the irradiation of the entire nipple-areola complex. The total irradiation procedure takes a few minutes. Further information is available online in the article by Professor Umberto Veronesi and Prof. Stefano Zurrida, creators of the ELIOT technique.