Treatment planning and techniques with the electron beam

The experience gained in the Department of Radiotherapy at the M.D. Anderson Hospital and Tumor Institute since the 7-18 MeV Siemens betatron was installed 16 years ago and the 17-25 MeV Sagittaire linear accelerator became available 7 years ago provides some insight into the importance of the electron beam in radiation therapy. The place of the electron beam among the various therapeutic modalities available to the radiation therapist today is most clearly defined in terms of its level of usefulness in a spectrum of clinical situations. When large areas of the skin need to be irradiated because of being potentially infiltrated, it is difficult and may be impossible to cover the total area with a photon beam, even utilizing a sophisticated treatment plant. In lateralized lesions, such as those of the buccal mucosa or retromolar trigone, the use of megavoltage photon-wedged fields will spare the opposite side of the oral cavity, but this technique is fraught with complications. Either there is a sharp gradient in dose between the minimal tumor dose and the dose to the mandible or, in order to obtain a minimal dose difference and not overdose the mandible, a long segment of the mandible must be irradiated. The electron beam, alone or combined with photons, can provide a superior dose distribution with a significant decrease in the high-dose volume