Assessment of the absorbed doses in the fetus from the computed tomography of the chest for the pregnant women

Abstract

The number and contribution of high dose imaging modalities, computed tomography in particular, is rapidly increasing both in the 'Russian Federation and other developed countries. Maximal increase in the number of computed tomography examinations in Russia was observed in 2020 due to the full-scale application of this imaging modality for the diagnostics of the novel coronavirus infection COVID-19. The use of computed tomography for the examination of the chest for the pregnant women is associated with several issues. An internationally accepted approach for the provision of the radiation safety of the pregnant patients is the assessment of the absorbed dose in the fetus after each X-ray examination. However, there are no existingn approved methods for the assessment of the absorbed dose in the fetus in the Russian Federation. The aim of the current study was to assess the doses in the fetus for the pregnant women undergoing computed tomography of the chest due to the COVID-19 and to estimate the probability of the development of the deterministic effects for the fetus. The study was based on the collection of the parameter of Russian and international computed tomography protocols. Parameters of the international computed tomography protocols were collected viameta-analysis of the existing publications; Russian protocols — via data collection in computed tomography departments in St-Petersburg hospitals. Absorbed dose in the uterus of the female patient and effective dose for the fetus were calculated using NCICT 3.0 software for 8, 10, 15, 20, 25, 30, 35 and 38 weeks of pregnancy. The results of the calculations indicate the lack of significant differences between absorbed doses in the uterus and effective doses for the fetus for all stages of pregnancy. Maximal doses for the selected computed tomog­ raphy protocols were in the range of 0.5 mGy (mSv) for 8-25 weeks, 0.6 mGy (mSv) for 30 week, 1.4 mGy (mSv) for 35 week and 2.7 mGy (mSv) for 38 week. The threshold for the development of the deterministic effects equal to 100 mGy cannot be exceeded even for repeated (10-15) computed tomography chest scans. Hence, the use of computed tomography as the primary method of COVID-19 diagnostics and staging will not be associated with the development of deterministic effects in the fetus.