An exploration of the potential utility of fetal cardiovascular MRI as an adjunct to fetal echocardiography

Abstract

ObjectivesFetal cardiovascular magnetic resonance imaging (MRI) offers a potential alternative to echocardiography, although in practice, its use has been limited. We sought to explore the need for additional imaging in a tertiary fetal cardiology unit and the usefulness of standard MRI sequences.MethodsCases where the diagnosis was not fully resolved using echocardiography were referred for MRI. Following a three‐plane localiser, fetal movement was assessed with a balanced steady‐state free precession (bSSFP) cine. Single‐shot fast spin echo and bSSFP sequences were used for diagnostic imaging.ResultsTwenty‐two fetal cardiac MRIs were performed over 12 months, at mean gestation of 32 weeks (26–38 weeks). The majority of referrals were for suspected vascular abnormalities (17/22), particularly involving the aortic arch (n = 10) and pulmonary vessels (n = 4). Single‐shot fast spin echo sequences produced ‘black‐blood’ images, useful for examining the extracardiac vasculature in these cases. BSSFP sequences were more useful for intracardiac structures. Real‐time SSFP allowed for dynamic assessment of structures such as cardiac masses, with enhancement patterns also allowing for tissue characterisation in these cases.ConclusionsFetal vascular abnormalities such as coarctation can be difficult to diagnose by using ultrasound. Fetal MRI may have an adjunctive role in the evaluation of the extracardiac vascular anatomy and tissue characterisation. © 2016 The Authors. Prenatal Diagnosis published by John Wiley & Sons, Ltd.

Prenatal diagnosis and clinical implications of an apparently isolated right aortic arch

“…In this variant, the left subclavian and left carotid arise separately from a diminutive left arch (which may be mistaken for an innominate artery) and a portion, usually the distal, of the left aortic arch is a thread‐like vestigial structure without luminal patency. This partial left aortic arch cannot be diagnosed on postnatal echocardiography but can only be visualized on direct inspection during surgery or suspected with fetal echocardiography or with 3D sequences from fetal cardiac MRI, which is utilized in our institution …”

Fetal cardiac cine imaging using highly accelerated dynamic MRI with retrospective motion correction and outlier rejection

“…When viewed from the perspective of acceleration by undersampling, the upper limit on the acceleration factor was set by the ratio of the full maternal field of view in the phase‐encode direction to the size of the fetal heart. Imaging parameters were selected with reference to previous MRI studies of the fetal heart using segmented cine and real‐time bSSFP, and were optimized to yield adequate signal and contrast to depict the fetal heart and surrounding anatomy with sufficient temporal resolution to capture cardiac pulsation during preliminary pilot cases not included in this report . Single‐slice imaging was performed with the following sequence parameters: repetition time (TR)/echo time (TE) 3.8/1.9 ms; flip angle 60 °; field of view 400 × 304 mm; voxels 2 × 2 × 6 mm; acceleration factor 8; and temporal resolution 72 ms. Operation was constrained to 2 W/kg or less whole body‐specific absorption rate, and low peripheral nerve stimulation and gradient‐induced acoustic noise settings were used.…”

MR imaging of the fetal heart

“…SSFP sequences were more useful for intracardiac structures. Real‐time SSFP allowed for dynamic assessment of structures such as cardiac masses, with enhancement patterns also allowing for tissue characterization in these cases …”

“…However, it may be limited by fetal position, oligohydramnios, overlying bone, and obesity. The diagnostic role of fetal MRI, as a complementary second level tool useful when the ultrasound is hampered by inadequate acoustic window, has recently been proposed by several groups . In a prospective single‐center study, a combination of SSFP and SS‐T 2 ‐TSE sequences identified the same diagnosis as postnatal findings in 79% of fetuses with CHD at a mean gestational age of 25.5 weeks .…”

“…The appealing versatility of cardiac MRI has driven advances in imaging technology which have overcome some of the challenges associated with imaging the fetus, prompting an increasing number of groups to investigate the potential of this imaging modality for assessing fetal cardiovascular and placental pathophysiology. In common with ultrasound, MRI can now precisely define cardiac anatomy, and for this purpose MRI is now regularly used in some centers to define the fetal cardiovascular morphology in the setting of congenital heart diseases (CHD) when a comprehensive diagnosis cannot be achieved using ultrasound . Cardiac MRI also provides an opportunity to collect unique information about the impact of cardiac malformations and placental dysfunction on fetal cardiovascular physiology.…”