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CC BY-NC-ND 4.0 · World J Nucl Med 2021; 20(04): 342-348
DOI: 10.4103/wjnm.WJNM_122_20
Original Article

Investigation of fetal absorbed dose in V/Q scan in three trimesters of pregnancy using Monte Carlo simulation

Shahabeddin Vakili
Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
,
Daryoush Shahbazi-Gahrouei
Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
,
Parastoo Pourasbaghi
1   Department of Medical Physics, School of Medicine, Tarbiat Modares University, Tehran, Iran
,
Elham Raeisi
2   Department of Medical Physics and Radiology, School of Allied Medical Sciences, Shahrekord University of Medical Sciences, Shahrekord, Iran
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Abstract

The ventilation/perfusion (V/Q) single-photon emission computed tomography is the first method of diagnosis for pulmonary embolism in pregnant women. This study aimed to calculate the fetal absorbed dose and compare to recommended values in V/Q scan at three trimesters of pregnancy by Monte Carlo simulation (code MCNPX) using simulated phantoms, based on the adult female MIRD phantom. The collection of pregnant women phantoms (that of Stabin) was designed with changes in the MIRD phantom. Source organs were defined for each of the radiopharmaceuticals used in two scans, 133Xe and 81mKr for the lung and bladder and technetium diethylene-triamine-pentaacetate (99mTc-DTPA) aerosol for lung ventilation scan. Also, technetium macroaggregated albumin (99mTc-MAA) for lung ventilation scan, lung, bladder, and liver. Fetal absorbed dose was calculated and evaluated for the administration radiopharmaceuticals using the MCNP simulation output. For 200 MBq 99mTc-MAA, fetal absorbed dose was 1.01–1.97 mGy, which is higher than the values recommended by International Commission on Radiological Protection (ICRP). The same fetal absorbed dose was found for activities of 54 and 70 MBq in the third trimester. For 99mTc-DTPA-aerosol, fetal absorbed dose as a ventilation tracer was within the permitted range. For 133Xe and 81mKr, it was negligible. It is concluded that the fetus received the highest absorbed dose in the third trimester of pregnancy. For this reason, in this period of pregnancy, it is recommended to use the lower administration activity and her awareness must be done.

Keywords

Absorbed dose - fetus - Monte Carlo simulation - ventilation-perfusion scan

Financial support and sponsorship

This work was financially supported (Grant No: 397555) by Isfahan University of Medical Sciences, Isfahan, Iran.




Publication History

Received: 05 October 2020

Accepted: 25 October 2020

Article published online:
24 March 2022

© 2021. Sociedade Brasileira de Neurocirurgia. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commecial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/)

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