Total body irradiation techniques and dosimetry.

Irradiation techniques and dosimetric methods used for total body irradiation (TBI) performed at Institut Gustave Roussy (Villejuif) are presented. TBI are performed in a 5,6 MV X-ray beam produced by a linear accelerator Neptune. The patient, lying laterally on a couch at 4.20 m from the target, is irradiated by a horizontal beam with a mean nominal dose rate at the abdomen mid-plane of about 9 cGy per minute. The procedure used for TBI consists of three parts in order to deliver 8 Gy in the whole body except for lungs which are protected with a lead screen during a part of irradiation and receive a dose of 4 Gy. We have preferred using "in vivo" measurements methods rather than calculations to determine the doses at different points of the patients. Two kinds of detectors are placed on the patient's skin all along the total body irradiation : two sets of five Therados semi conductors probes permit to control the irradiation and lithium fluoride thermoluminescent dosimeters are used like reference detectors. The dosimetric results obtained during the TBI performed at IGR are discussed.