Magnetic resonance imaging of the fetal brain.
BACKGROUND
This review covers the recent literature on fetal brain magnetic resonance imaging, with emphasis on techniques, advances, common indications, and safety.


METHODS
We conducted a search of MEDLINE for articles published after 2010. The search terms used were "(fetal OR foetal OR fetus OR foetus) AND (MR OR MRI OR [magnetic resonance]) AND (brain OR cerebral)". Consensus statements from major authorities were also included. As a result, 44 relevant articles were included and formed the basis of this review.


RESULTS
One major challenge is fetal motion that is largely overcome by ultra-fast sequences. Currently, single-shot fast spin-echo T2-weighted imaging remains the mainstay for motion resistance and anatomical delineation. Recently, a snap-shot inversion recovery sequence has enabled robust T1-weighted images to be obtained, which is previously a challenge for standard gradient-echo acquisitions. Fetal diffusion-weighted imaging, diffusion tensor imaging, and magnetic resonance spectroscopy are also being developed. With multiplanar capabilities, superior contrast resolution and field of view, magnetic resonance imaging does not have the limitations of sonography, and can provide additional important information. Common indications include ventriculomegaly, callosum and posterior fossa abnormalities, and twin complications. There are safety concerns about magnetic resonance-induced heating and acoustic damage but current literature showed no conclusive evidence of deleterious fetal effects. The American College of Radiology guideline states that pregnant patients can be accepted to undergo magnetic resonance imaging at any stage of pregnancy if risk-benefit ratio to patients warrants that the study be performed.


CONCLUSIONS
Magnetic resonance imaging of the fetal brain is a safe and powerful adjunct to sonography in prenatal diagnosis. It can provide additional information that aids clinical management, prognostication, and counselling.
Department of Diagnostic and Interventional Radiology, Kwong Wah Hospital, Yaumatei, Hong Kong.
L Mf
LM
Tee
Department of Diagnostic and Interventional Radiology, Kwong Wah Hospital, Yaumatei, Hong Kong.
E Yl
EY
Kan
Department of Diagnostic and Interventional Radiology, Kwong Wah Hospital, Yaumatei, Hong Kong.
J Cy
JC
Cheung
Department of Obstetrics and Gynaecology, Kwong Wah Hospital, Yaumatei, Hong Kong.
W C
WC
Leung
D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging*; D056324:Diffusion Tensor Imaging; D005260:Female; D005315:Fetal Diseases / Q000000981:diagnostic imaging*; D005333:Fetus / Q000000981:diagnostic imaging*; D005865:Gestational Age; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000009:adverse effects / Q000379:methods*; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*
Brain/embryology; Magnetic resonance imaging; Prenatal diagnosis