Reproduction of set-up of the fields in x-ray radiotherapy

We measured the reproducibility of the field in radiotherapy by lineacgram and carried out the measurement of the following sites such as the larynx, pharynx, whole brain and the whole pelvis. The measurement points are 5 in the head and neck, and 7 in pelvis. The data of this study were obtained from 536 film sheets for 62 patients during May 1983 to September 1983 period. We used the XTL-5 localization film and Kyokko GF intensifying screen. The reproducibility error was decided with the use of the average and standard deviations. The following results were obtained: 1) The site that has the minimal error is larynx with 4.8 mm; the maximal error is whole brain with 11.2 mm; and the whole pelvis with 6 mm. 2) The fixing device is always needed at the head and neck site. 3) Using the fixing device, it was comfirmed that the reproducibility error of the field is due to arrangement of place rather than the patients movement during the treatment time. We further aim, to reduce the scattering shown by the standard deviation than the one by the average value. (author)