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In utero MRI diagnosis of a complex congenital cardiac malformation

Case Study
Prof. Saleem, Sahar, MBBCh, MSc, MD Kasr Al-Ainy-Cairo University Egypt

Patient history

A 24-year-old lady presented at 30 weeks' gestation with query fetal heart abnormalities at ultrasonographic study. Difficulties encountered in fetal echocardiography in this patient were artifacts caused by bone ossification due to advanced gestation as well as persistent anterior position of the fetal back.

Imaging parameters

MRI was performed in the same day of Ultrasonography study using a 1.5 T superconducting magnet (Gyroscan Intera; Philips, Best, The Netherlands) and a phased-array surface coil. Balanced Steady state free precession sequences (b-SSFP=b-FFE) were obtained using repetition time (TR): 3.5-4 ms, echo time (TE): 1.7-2 ms, Flip angle (FA): 60-90°, and 5 mm slice thickness with section overlap of -2mm. The number of signal averages (NSA) was 2-4.The scan time of each sequence depended on the number of slices and NSA; typically 16 seconds were needed to obtain 16 slices using 2 signal averages. b-FFE was acquired during free maternal breathing. After a scout acquisition was performed, a series of images along the 3 fetal body planes (axial, sagittal and coronal) were obtained. Each new acquisition was prescribed by using images from the immediately prior acquisition to avoid the misregistration caused by fetal movement. Additional MR images were obtained along cardiac axes. From the coronal plane, the long axis view was obtained along a line that extended from the cardiac apex to the mid of the left ventricle (LV). Short axis view was obtained perpendicular to the long axis. In the short axis view, the image where LV is concentric and right ventricle (RV) is crescent-shaped was chosen to align the plane for the 4-chamber view which extended along the LV centre of to the furthest corner of the RV. From the 4-chamber image, the two-chamber view was obtained along the right and left heart.
Axial b-FFE four chamber view of fetal heart Cardiomegaly with its axis directed to the left. A large atrio-ventricular septal defect (arrow). Mild pericardial effusion (arrowhead)Sagittal b-FFE  of fetal heart Parallel course of the great arteries at their origin indicating TGA: Transposition of the great arteries. The aorta  (arrow) originates from the right ventricle anteriorly, and the pulmonary artery (arrowhead) from the left ventricle posteriorlyCoronal b-FFE of fetal heart Parallel course of the great arteries at their origin (arrowheads) indicating Transposition of great arteries (TGA) )
Axial b-FFE four chamber view of fetal heart
Sagittal b-FFE of fetal heart
Coronal b-FFE of fetal heart
Cardiomegaly with its axis directed to the left. A large atrio-ventricular septal defect (arrow). Mild pericardial effusion (arrowhead)
Parallel course of the great arteries at their origin indicating TGA: Transposition of the great arteries. The aorta (arrow) originates from the right ventricle anteriorly, and the pulmonary artery (arrowhead) from the left ventricle posteriorly
Parallel course of the great arteries at their origin (arrowheads) indicating Transposition of great arteries (TGA) )

Diagnosis

In-utero MRI using b-FFE identified well the morphology of the fetal heart. Four-chamber transverse view of the heart enables assessment of the enlarged cardiac size, normal left cardiac axis as well as the large atrioventricular septal defect. Coronal and sagittal planes identify the relative position of the ventricular outflow tracts at their origin to be parallel rather than perpendicular. This finding indicates transposition of the great arteries (TGA). Note also the presence of a rim of pericardial effusion.

Impact of imaging

Although echocardiography is the gold standard diagnostic imaging tool for prenatal detection of cardiac malformations, the modality is occasionally limited by acoustic windows, poor images of the distal vasculature, fetal position, maternal adipose tissue, abdominal wall scar form previous abdominal or pelvic surgery, and bone artifacts in advanced gestation. In this case with US technical difficulties, proper MRI study surpassed echocardiography in assessment of fetal cardiac malformation


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Feb 3, 2011

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Case Study
Intera 1.5T
4-chamber view, B-FFE, Cardiac, Pediatric
 

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