Fetal dose for a patient undergoing mantle field irradiation for Hodgkin's disease.

In order to safely treat a 23 weeks pregnant woman for supradiapharagmatic Hodgkin's disease, without compromising the fetus, a custom shielding table was constructed and extensive phantom measurements were performed. For 10 MV photons, the optimal shielding combination was found to consist of a 5 cm thick lead sheet placed onto a 1.25 cm aluminum supporting plate. The structure was placed directly above the phantom, over the region corresponding to the woman's abdomen, without any intervening air gap. By this means the dose to the fetus from machine leakage and collimator scatter was eliminated; the only remaining dose was due to in-phantom scatter. The woman was treated using a mantle field to a dose of 35 Gy in 20 fractions. The accumulated dose to the woman's uterine fundus and to her pubis were monitored with theroluminescent dosimeters. After completion of mantle therapy the doses to the fundus and pubis were 10 and 3 cGy, respectively. The fetal exposure was thus limited to below 10 cGy, within the zone of fetal tolerance. A normal infant was delivered at term.