Fetal MRI in the Third Dimension by ProQuest

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									Fetal MRI in the Third Dimension

Jeffrey C. Hellinger, MD, and Monica Epelman, MD

         iagnostic fetal imaging is an
         essential requirement for pre-
         and post-natal care and out-
come. Imaging may be applied for
screening, targeted evaluations and sur-
veillance of fetal abnormalities. Ultra-
sound (US) historically has been and
remains the principle obstetrical imag-
ing modality. It is readily performed in
outpatient and inpatient settings at mini-
mal inconvenience to the mother, yield-
ing reliable information for immediate
clinical counseling and management.
Initial sonographic screening of all
body systems occurs between 20 and 24
weeks. Standard protocols are per-
formed with 2-dimensional grayscale            sional ultrasound has gained increased        ited ability to perform comprehensive
and Doppler static and cine techniques         application over the past several years,      functional evaluations, however, rele-
to generate structural and functional          improving structural display1 and             gates MRI to an adjunctive role, after
information. Inherent limitations              affording volumetric quantitative analy-      ultrasound has been performed. MRI is
include operator and acoustic window           sis.2 Clinical benefit in diagnosis, treat-   often requested to provide more defini-
dependence. In addition, interpretation        ment planning, and family counseling          tive anatomical understanding and
is based upon a summation of the               has been reported for evaluation of           diagnosis for abnormalities identified
images and cine loops from multiple            facial abnormalities, neural tube             on the screening ultrasound, as well as
real-time projections. Three-dimen-            defects, skeletal defects, congenital         to assess for concomitant abnormali-
                                               heart disease and the central nervous         ties.5 The literature has also advocated
    Dr. Hellinger is Associate Professor of    system1 as well as fetal biometry.3 With      its use for anatomical screening in the
    Radiology and Pediatrics and Director      improved operator experience, clinical        setting of congenital heart disease
    of the Advanced Imaging and Informat-      workflow is enhanced.4                        (CHD)6 and predisposed families.7
    ics Laboratory, Departments of Radiol-        Magnetic resonance imaging (MRI)              Standard MRI protocols utilize high
    ogy and Pediatrics, Stony Brook Long       has become an important secondary             resolution, ultra-fast static and dynamic
    Island Children’s Hospital, Stony Brook
    University School of Medicine, Stony
                                               obstetrical modality for both the fetus       cine 2-dimensional T1- and T2-
    Brook, NY; and Dr. Epelman is Assis-       and the mother. Compared with ultra-          weighted (T1W and T2W) sequences.8,9
    tant Professor of Radiology, Director of   sound, it offers superior spatial resolu-     Using 2-dimensional MRI, multiple
    Neonatal Imaging, Department of Radi-      tion and structural detail, affording         acquisitions, in multiple planes are often
    ology, The Children’s Hospital of          comprehensive anatomical displays             required to ensure complete anatomical
    Philadelphia, University of Pennsylva-     from single acquisitions. The high            coverage. The number of acquisitions
    nia School of Medicine, Philadelphia,      cost, potentially long exam time in a         and the exam time are directly depen-
                                               typical closed bore unit, and the lim-        dent upon fetal movement, with the total

8      ■    APPLIED RADIOLOGY     ©
                                      www.appliedradiology.com                                                        July–August 2010
                                                                                             FETAL MRI IN THE THIRD DIMENSION

FIGURE 1. Normal 3-dimensional SSFP FMRI multiplanar interrogation. Depending upon the image quality, a single 3-dimensional SSFP
sequence can be manipulated using MPR (B,D,F) and thin-slab MIP (A,D,E,G-J) to generate anatomical images of the placenta (A, asterisks);
brain (B); ventricular system and spinal canal (C); vertebral bodies (D); airway and lungs (E); heart (F); stomach and small bowl (G-H); kidneys,
ureters, and bladder (I); and extremities (J).

                                                                                                   number of sequences often ranging
                         Table 1. 3D Fetal MRI Sequences                                           between 20 to 25, yielding an average
      3D (T1) Volume Interpolated GE                3D (T2 / T1) Balanced SSFP                     exam time of 30 to 55 min. As with ultra-
                                                                                                   sound, interpretation is often based upon
            Meconium                                     Amniotic Fluid
                                                                                                   mental reconstruction of the anatomy
            Hemorrhage                                   Placenta and Umbilical Cord
            Placenta                                     Central Nervous System                    and pathology from the multiple acquisi-
            Colon                                        Craniofacial and Neck                     tions; communication, treatment plan-
            Liver                                        Thorax (including airway)                 ning and family counseling frequently
            Spleen                                       Cardiovascular                            require displaying multiple sequences.
            Thryoid Gland                                Gastrointestinal                             Three-dimensional MRI sequences
            Pituitary Gland                              Genitourinary                             can also be acquired through the gravid
                                                         Musculoskeletal                           pelvis (Table 1, Figures 1 and 2) with
  GE = Gradient Echo; SSFP = Steady State Free Precession                                 
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