MR Imaging of the Fetus in Utero I: A Practical Guide to Systematic Analysis - Central

A Robinson, S Blaser, A Toi, M Gundogan, S Pantazi, D Chitayat , G Ryan The Hospital for Sick Children Departments of Diagnostic Imaging and Clinical & Metabolic Genetics Mount Sinai Hospital Departments of Medical Imaging, Prenatal Diagnosis & Medical Genetics and Obstetrics & Gynaecology The University of Toronto, Ontario, Canada

Purpose Check cranial vault, BPD & HC Check orbits Check sulcation & gyration Check spine Well-established protocols exist for the sonographic examination of the fetus, encompassing differing levels of detail depending on the overall risk of the individual pregnancy (i.e., from a routine screening examination up to a tertiary-level P P detailed assessment of a high-risk pregnancy). No such protocols are established yet for fetal MR imaging. In our institution we have attempted to establish a protocol for reporting fetal MR examinations, in order that a systematic and methodical approach is adopted by our radiologists, including those who are not used to reading these examinations. The expectation is that by having a protocol for MR assessment, we would avoid missing important anatomical abnormalities.

Ultrasound protocols P We compiled a chart of the amalgamated current guidelines for sonographic assessment of the fetus from several insitutions – Biparietal & occipito-frontal P The American College of Radiologists, The Association for Ultrasound in Medicine, The American College of Obstetricians and diameters ExampleExample – plane - Abnormal too high Binocular distance Interocular distance Normal spine Example – Gynecologists, the Society of Obstetricians and Gynecologists of Canada, the Canadian Association of Radiologists, and the Parieto-occipital fissure (P) Royal College of Obstetricians and Gynecologists (UK). This chart is presented below. It is interesting to note the Correct plane=cavum anterior, Cavum vergae included (not Binocular distance (BOD) is Interocular distance (IOD) is Parieto-occipital fissure also should be assessed with Sacral lipomyeloschisis -seen on medial aspect of discrepancies. tentorial hiatus posterior cavum septum pellucidum) measured between the two measured between the two seen on coronal view of amniotic fluid between fetus - cord was elongated and -BPD measured from inner and tentorial hiatus not malar margins of each vitrous. ethmoidal margins of each posterior cortex on axial view posterior cortex and the uterine wall. entering defect. table to outer table of skull included vitreous. -appears 22-23 weeks -OFD measured outer to outer ACR -HC=(OFD+BPD)/2*π AIUM RCOG INSTITUTION ACOG SOGC CAR (UK) Name  P Medical Record Number  Indication  Referring physician  Last Menstrual Period (LMP)  Exam date  Transcription date  C Reporting physician  C C Cardiac Activity   Rate  Ocular diameter Example - PHPV Example – neurenteric cyst Example - teratoma Rhythm  Number of gestations   Ocular diameter (OD) Microphthalmia, hypertelorism Calcarine fissure also seen on Chorionicity & amnionicity   Example – Example – exencephaly Calcarine fissure (C) Patent canal of Kovalevsky Large mixed solid/cystic Presentation of fetus   measured between malar and persistent hyperplastic primary -seen on medial aspect of parasagittal view through of clearly seen. . Activity of fetus  Cranium & brain absent Cranium absent ethmoidal margins of vitrous vitreous in trisomy 22 posterior cortex medial cortex Amniotic fluid volume    Check ventricular atrium & choroid plexus -can be calculated: -appears at 24-25 weeks. - also shows parieto-occipital Placenta Location    OD=(BOD-IOD)/2 fissure. Check ears – external, middle and internal Appearance   Internal os    (GA) Biparietal daimeter (BPD)     Head circumference (HC)     Check facial profile & lips Femur length (FL)     Abdominal circumference (AC)     Estimated fetal weight (EFW)   Maternal anatomy Uterus    R Adnexae    R Head & neck Cranium       Choroid plexus   Cisterna magna     Example – large atrial Ventricular atrium (VA)     Ventricular atrium width diameter Falx  Normal ears Example– cup ears Cavum septum pellucidum  *    Correct plane = slightly above Microlissencephaly Face Rolandic (central) sulcus (R) Lips   BPD/HC plane -dilated ventricles Rolandic sulcus often better External auditory meati normal Cup ear deformity in fetus with Normal profile Example – Pierre-Robin -seen on superolateral aspect of Chest 4 chamber heart     -perpendicular to lateral wall -choroid dangling to seen on parasagittal view Pinnae normal multiple congenital anomalies Situs  cortex on axial view -just behind the choroid dependent side. Outflow tracts    Lips and anterior alveolar Severe retrognathia & --appears at 26-27 weeks Axis  plexus. margins should be in obstruction of hypopharynx by Diaphragm   alignment on the sagittal view the tongue Abdomen Stomach Presence     Check cerebellum & cisterna magna Size  Situs   Kidneys     Bladder     S Cord insertion     Cord vessels     Spine     Extremities Upper Arm     Hand    T Lower Leg     Foot    Example – microtia Gender    Cerebellar diameter & Example - Normal cochlea in trisomy 22 *=mentioned in correct level for BPD assessment but not specifically cisterna magna depth Example – Dandy-Walker NormalNormal maxilla maxilla & nostrils Example – cleft lip & palate Superior temporal sulcus (T) 29 week fetus with no Sylvian Useful to exclude branchial Pinnae small/absent with no arch syndromes from isolated connection to middle ear Correct plane = slightly below -vermis displaced superiorly & Alveolar ridge continuous Cleft seen in lip and hard -seen on lateral aspect of cortex fissure or other fissures that Proposed MR protocol retrognathia structures BPD & HC IV ventricle expands into across midline palate on coronal view should be seen by this stage We found that there was significant inter and intra-institutional variation in the quality of the antenatal sonographic assessment. -tilted into posterior fossa posterior fossa -appears at 29 (27-32) weeks Other factors that particularly affected the antenatal sonographic assessment included maternal obesity, late gestational age -Sylvian fissure also seen Suggested reading and oligohydramnios. Check cerebellar vermis •Garel C. Chantrel E. Brisse H. et al. Fetal : normal Check midline structures gestational landmarks identified using prenatal MR imaging. Ajnr: We felt that in these situations, the minimum standard for antenatal MR assessment should be the same as for antenatal US American Journal of Neuroradiology. 22(1):184-9, 2001 Jan. assessment. However we appreciate that certain structures cannot be readily assessed by current antenatal MR techniques, •Garel C. Chantrel E. Elmaleh M. et al. Fetal MRI: normal gestational for example cardiac anatomy and great vessels, whereas other structures are more readily assessed by MR, for example the landmarks for cerebral biometry, gyration and myelination. Childs posterior fossa and sagittal brain anatomy, particularly if skull ossification in later gestation inhibits US assessment. Nervous System. 19(7-8):422-5, 2003 Aug. We adopted the amalgamated guidelines for sonographic assessment, and follow them as far as is possible when performing •Levine D. Trop I. Mehta TS. et al. MR imaging appearance of fetal MR assessment. We demonstrate a practical guide to analysis of the central nervous system of the fetus in utero, including cerebral ventricular morphology. Radiology. 223(3):652-60, 2002 Jun. how to perform the biometric measurements, and examples of normal and abnormal biometry and development. •Twickler DM. Reichel T. McIntire DD. et al. Fetal central nervous system ventricle and cisterna magna measurements by magnetic Vermian craniocaudal Example – inferior vermian resonance imaging. American Journal of Obstetrics & Gynecology. Materials & Methods diameter hypoplasia 187(4):927-31, 2002 Oct. Example– septo-optic Example– ExampleExample––frontonasalfrontonasal •Reichel TF. Ramus RM. Caire JT. et al. Twickler DM. Fetal central Retrospective analysis was performed in over 190 consecutive fetal MR examinations performed for CNS and non-CNS Midline sagittal plane -overall diameter too small dysplasia Example– callosal agenesis dysplasiadysplasia nervous system biometry on MR imaging. AJR. American Journal of indications. Analysis included, but was not limited to, biometry, including biparietal diameter, transcerebellar diameter, -primary fissure and declive and too little tissue below Roentgenology. 180(4):1155-8, 2003 Apr. ventricular atrial width, craniocaudal diameter of the cerebellar vermis, the presence of the cavum septum pellucidum and seen posteriorly fastigium Cavum absent - fornices fused Monoventricle “Steerhorn” lateral ventricles Cleft lip & callosal agenesis corpus callosum and other midline and lateral structures, cortical development and appearance of sulci and major fissures.