Knowledge of doses from radiumtherapy for skin hemangioma in childhood

Before 1974 about 5000 children were irradiated at the Institut Gustave-Roussy for a skin hemangioma of whom 20% were treated with radium applicators. To evaluate the absorbed doses to these patients at any site, we have developed a software program which permits simulation of the actual patient and treatment conditions. Part of this software is devoted to constructing an Individual Computerized Tomography Anatomy (ICTA) based on real human transverse slices and auxological tables. From the generated phantom, 160 anatomical sites of epidemiological interest are defined and localized according to a Cartesian co-ordinate system. The gamma doses at all sites from Ra-226 applicators are calculated by an algorithm which permits separation of the radiation paths in air, tissue, and lungs. It includes a correction for attenuation and scatters in infinite and semi-infinite mediums. To evaluate the factor φ(r) for these corrections at any distance or position from the applicator, we have modelled the results from several Monte Carlo simulations. In the range of 1 to 10 cm, the φ(r) values obtained from our model showed good agreement with those obtained by published methods. For several cases, the absorbed doses at points in water and patients from radium applicators estimated by this software, were compared to those measured and estimated at the Karolinska Hospital. The results showed good agreement. (author)