Title:
Prediction of Specific Absorption Rate in Mother and Fetus Associated With MRI Examinations During Pregnancy
Author(s):
J.W. Hand, Y. Li, E.L. Thomas, M.A. Rutherford and J.V. Hajnal
Source:
Magnetic Resonance in Medicine
Vol./Issue/Date:
Volume 55
Year:
2006
Page(s):
883–893
Keywords:
SAR; safety; fetus; pregnant; 28 weeks’ gestation
Abstract:
There is uncertainty regarding the risk posed by magnetic resonance
imaging (MRI) examinations to pregnant patients. The
most frequently used methods, such as single-shot fast spin
echo (ssFSE), often require operation at the specific absorption
rate (SAR) limits imposed by safety guidelines. With the introduction
of higher-field systems, such limits will be even more
significant for fetal imaging. An electromagnetic solver based
on the time domain finite integration technique (FIT) was used
to predict SAR in an anatomically realistic model of a pregnant
patient (28 weeks’ gestation) associated with the radiofrequency
(RF) fields from birdcage body coils typical of 1.5 T and
3 T MRI systems (i.e., operating at approximately 64 and
127 MHz, respectively). The results suggest that 1) the highest
local SAR is in the mother, with the fetus being exposed to a
peak of approximately 40–60% of that value at 64 MHz, increasing
to approximately 50–70% at 127 MHz; 2) compliance with
U.S. Food and Drug Administration (FDA) and International
Commission on Non-Ionizing Radiation Protection (ICNIRP)
guidelines requires control of SAR values averaged over 1 g or
10 g of tissue, respectively; and 3) compliance with Medical
Device Agency (MDA) guidelines requires control of the maximum
SAR10g within the fetus. Magn Reson Med 55:883– 893,
2006. © 2006 Wiley-Liss, Inc.
Document:
Reference Id:
29
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