Estimation of the radiation dose from radiotherapy for skin haemangiomas in childhood: the ICTA software for epidemiology

Radium applicators and pure beta emitters have been widely used in the past to treat skin haemangioma in early childhood. A well defined relationship between the low doses received from these applicators and radiation-induced cancers requires accurate dosimetry. A human-based CT scan phantom has bee n used to simulate every patient and treatment condition and then to calcul ate the source-target distance when radium and pure beta applicators were u sed. The effective transmission factor phi ((r)) for the gamma spectrum emi tted by the radium sources applied on the skin surface was modelled using M onte Carlo simulations. The well-known quantization approach was used to ca lculate gamma doses delivered from radium applicators to various anatomical points. For P-32, Sr-90/Y-90 applicators and Y-90 needles we have used the apparent exponential attenuation equation. The dose calculation algorithm was integrated into the ICTA software (standing for a model that constructs an Individualized phantom based on CT slices and Auxological data), which has been developed for epidemiological studies of cohorts of patients who r eceived radium and beta-treatments for skin haemangioma. The phi ((r)) valu es obtained for radium skin applicators are in good agreement with the avai lable values in the first 10 cm but higher at greater distances. Gamma dose s can be calculated with this algorithm at 165 anatomical points throughout the body of patients treated with radium applicators. Lung heterogeneity a nd air crossed by the gamma rays are considered. Comparison of absorbed dos es in water from a 10 mg equivalent radium source simulated by ICTA with th ose measured at the Radiumhemmet, Karolinska Hospital (RAH) showed good agr eement, but ICTA estimation of organ doses did not always correspond those estimated at the RAH. Beta doses from P-32, Sr-90/Y-90 applicators and Y-90 needles are calculated up to the maximum beta range (11 mm).