Pulmonary embolism in pregnant patients: fetal radiation dose with helical CT.
OBJECTIVE
To calculate mean fetal radiation dose from helical chest computed tomography (CT) by using maternal-fetal geometries obtained from healthy pregnant women and to compare the calculated CT doses with the fetal doses reported with scintigraphy.


METHODS
Maternal-fetal geometries were determined in 23 pregnant women with varying body mass index and fetal gestational age. Monte Carlo techniques were used to estimate the dose that would be received by each fetus from CT scanning performed with the following parameters: 120 kVp; 100 mA; scanning time, 1 second per section; collimation, 2.5 mm; pitch of 1. Craniocaudal extent of the scan was 11 cm, with the most caudal section edge being 5 mm inferior to the xiphoid process.


RESULTS
For helical CT, estimated mean fetal doses in micrograys at varying gestational ages were as follows: 3.3-20.2 microGy, first trimester; 7.9-76.7 microGy, second trimester; and 51.3-130.8 microGy, third trimester. These values were all less than mean fetal doses reported with scintigraphy, with 37-74 MBq of macroaggregates of human serum albumin labeled with technetium 99m. If 200 mAs (pitch of 1.8) was used, the mean fetal doses were still less than those with scintigraphy.


CONCLUSIONS
The average fetal radiation dose with helical CT is less than that with ventilation-perfusion lung scanning during all trimesters.
Winer-Muram
Helen T
HT
Department of Radiology, Indiana University School of Medicine, 550 N University Blvd, Indianapolis, IN 46202, USA. hwinermu@iupui.edu
Boone
John M
JM
Brown
Haywood L
HL
Jennings
S Gregory
SG
Mabie
William C
WC
Lombardo
Gerard T
GT
D000328:Adult; D000886:Anthropometry; D005260:Female; D005333:Fetus / Q000528:radiation effects*; D006801:Humans; D009010:Monte Carlo Method; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000000981:diagnostic imaging*; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; D014057:Tomography, X-Ray Computed