Program for Absorbed Dose Evaluation and Risk Assessment of Fetus Following Maternal Radioiodine Therapy

Abstract

Background and  Objective  :  Absolute contraindications for administration of radioiodine in nuclear medicine are pregnancy and lactation, because radioactive iodine can be transferred across the placenta and be secreted in breast milk. When ingested, it can cause radiation exposure to the infant.  The calculation of internal dose quantity according to MIRDOSE and the risk of radiation for fetus following the ICRP Publication 60 are strongly recommended for the suspected pregnancy after maternal radioiodine therapy especially in case of hyperthyroidism and thyroid cancer patients. This study aim to develop a computer program based on the IAEA standard accurately and rapidly calculate absorbed dose and assess the radiation risk for fetus whose mother was using radioiodine.

Material and method:  The program to embed libraries and steps of expected fetus absorbed dose and risk assessment in the computer code is written in Microsoft Excel 2010. The computerized values are then compared with those retrospective and manual calculations according to the experts accounting for 5 cases from 2005 to 2015.

Results :  From 5 cases of radioiodine treatment during pregnancy in Siriraj Hospital, the calculated fetus doses using the program are 377.4, 377.4, 0.21, 0.59 and 29.4 mGy respectively. Moreover, the risk assessment for fetus of all cases can be completely achieved.

Conclusion :  The comparison of the absorbed dose obtained from the two methods show the similar accuracy under IAEA standard. Besides, the program is not time-consuming and provides more information for risk assessment of fetus than the manual calculation.