Feasibility of Non-Gated Dynamic Fetal Cardiac MRI for Identification of Fetal Cardiovascular Anatomy

Abstract

Introduction: To evaluate the feasibility of identifying the fetal cardiac and thoracic vascular structures with non-gated dynamic balanced steady-state free precession (SSFP) MRI sequences. Methods: We retrospectively assessed the visibility of cardiovascular anatomy in 60 fetuses without suspicion of congenital heart defect. Non-gated dynamic balanced SSFP sequences were acquired in three anatomic planes of the fetal thorax. The images were analyzed following a segmental approach in consensus reading by an experienced pediatric cardiologist and radiologist. An imaging score was defined by giving one point to each visualized structure, yielding a maximum score of 21 points. Image quality was rated from 0 (poor) to 2 (excellent). The influence of gestational age (GA), field strength, placenta position, and maternal panniculus on image quality and imaging score were tested. Results: 30 scans were performed at 1.5T, 30 at 3T. Heart position, atria and ventricles could be seen in all 60 fetuses. Basic diagnosis (>12 points) was achieved in 54 cases. The mean imaging score was 16.8+/-3.8. Maternal panniculus (r=-0.3; p=0.015) and gestational age (r=0.6; p<0.001) correlated with imaging score. Field strength influenced image quality, with 1.5T being better than 3T images (p=0.012). Imaging score or quality were independent of placenta position. Discussion/Conclusion: Fetal cardiac MRI with non-gated SSFP sequences enables recognition of basic cardiovascular anatomy.

Utility of Fetal Cardiac Resonance Imaging in Prenatal Clinical Practice: Current State of the Art

“…The weaker field strength reduces the likelihood of potential heating effects on the fetus and decreases the risks associated with strong magnetic field exposure [15]. Geiger et al [21] reported that fetuses examined at 1.5 T obtained a significantly higher imaging quality than at 3 T because of lower sensitivity to motion artifacts and fewer inhomogeneities of the radiofrequency field. In conclusion, 1.5 T CMR is usually sufficient to perform fetal CMR.…”

“…If the signal intensity is not adequate, the coil must be repositioned accordingly. Scout sequences are obtained in the three orthogonal planes of the mother's abdomen (axial, sagittal, and coronal) using 6-8 mm single-shot fast spin-echo (SSFSE) T2-weighted sections with a 1-2 mm gap and a large field of view (320-400 mm) [21].…”

“…In addition, image quality of fetal CMR is not affected by oligohydramnios, late gestational age, maternal obesity, multiple gestations, placental position, or progressive calcification of the ribcage in late-gestation patients [11,21,27]. Fetal CMR can be a valuable diagnostic tool in cases of intrauterine growth restriction (IUGR), a condition in which a fetus fails to achieve its expected growth potential in the womb.…”

“…After birth, it can be easily obtained by using an ECG gating, while it is unavailable in fetuses [61][62][63]. Geiger et al [21] demonstrated that non-gated dynamic steady-state free-procession CMR sequences allow for elementary assessment of cardiovascular anatomy. To overcome this limit and to increase to expand the diagnostic capabilities of CMR, alternative methods have been developed.…”

“…Severe maternal obesity might limit the use of CMR as the patient would be too large for the CMR scanner, and since wider patient tables reduce image quality. In addition, claustrophobia and anxiety can lead to an increase in mothers' movements during scanning, thus resulting in motion artifacts, which lower a scan's quality and worsen its diagnostic value [21]. Sometimes scans may need to be stopped, in particular, by pregnant women in most advanced stages of pregnancy, who may not tolerate prolonged immobilization in closed spaces.…”