Techniques of experimental animal radiotherapy

Animal research is a crucial component of the generation of new knowledge in human and veterinary medicine. Total body irradiation, whole brain irradiation, total lymphoid irradiation, and local field irradiation of experimental animals are powerful tools for immunology, oncology, studies of normal tissue radiation tolerance, and medical physics. Animal radiotherapy requires specialized techniques. Because of necessarily smaller field sizes, beam localization must be particularly precise. Care must be taken to obtain optimum and accurate dose distribution. This requires consultation with a medical physicist. Optimum dose distribution may be obtained, depending upon the circumstance, by use of either a single beam or two parallel opposed beams with or without bolus. To ensure a proper dose to the animal target volume, care must be paid to the selection of beam energy and the use of radiation attenuators. Beams may be shaped by custom-made lead alloy blocks. Radiation dose rate may be modified by changing the linear accelerator output or the distance from the beam source to the animal, or by attenuating the beam. Reliable targeting of animals requires, for fields other than total body irradiation, anesthesia-utilizing agents such as ether, ketamine, and pentobarbital. The objective of this report is to review the techniques of experimental animal radiotherapy.