Estimation of foetal radiation dose in a comparative study of pelvimetry with conventional radiography and different computer tomography methods

Abstract

Introduction: Conventional radiography and computed tomography (CT) can result in different radiation doses to the foetus when pelvimetry needs to be performed before childbirth. New techniques in diagnostic imaging provide the basis for the optimization of radiation dose and create opportunities for higher measurement accuracy. The purpose of the study was to estimate the radiation dose to the foetus from pelvimetry performed using conventional radiography compared to different CT methods, namely: the topogram method, cross-sectional method, short-spiral method, standard-spiral method, and flash-spiral method. Methods: An anthropomorphic phantom and thermoluminescent dosemeters (TLD) were used for the dose measurements. Bags with sodium chloride were placed on top of the phantom’s abdomen and were used to simulate the last month of pregnancy. The foetal radiation dose was equated to the absorbed energy to the TLDs placed at the area of the birth canal (uterus). Results: The mean absorbed dose to the foetus was measured with conventional radiographic technique to 0.16mGy. The mean absorbed dose to the foetus with the various CT methods resulted in 0.17mGy (topogram), 0.21mGy (cross-sectional), 0.45mGy (short-spiral), 0.57mGy (standard-spiral), and 0.75mGy (flash-spiral). Conclusion: Although the absorbed dose to the foetus was higher in the CT pelvimetry methods, the dose levels are low. The CT spiral methods allowed adjustments in multiplane image reconstructions which could increase measurement accuracy. However, further studies are needed to investigate different CT pelvimetry methods in relation to measurement accuracy.