Abdominal dosimetry for supradiaphragmatic irradiation of Hodgkin's disease in pregnancy. Experimental data and clinical considerations.

An experimental dosimetry by an Alderson Phantom was carried out at the Istituto Nazionale Tumori of Milan to evaluate the scattered radiation in the abdomen for a radiotherapeutic treatment of some lymph node supradiaphragmatic regions. This information is very important when a radiological treatment of stage I and IIA Hodgkin's disease must be set up after the 3rd month of pregnancy. A dose of 3000 rad (30 Gy) was given to left supraclavicular and mediastinum as if involved by a lymphoma. A cobalt 60 unit and a 6 MeV linear accelerator were sequentially tested. Scattered radiation was measured by TLD dosimeters in multiple abdominal sections from diaphragm to pubis ever 5 cm. Scattered radiation was lower with the linear accelerator than with cobalt. Doses to the pelvis ranged from 3.5 rad to 6.3 rad for the linear accelerator. These values are not negligible but acceptable, because the risks of fetal malformation are very low after the third month of pregnancy.