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3D Visualization of the Fetal Heart Using Prenatal MRI
Study Questions:
How effective is prenatal magnetic resonance imaging (MRI) with motion-corrected slice-volume registration in the visualization of the fetal vasculature?
Methods:
A single-center cohort study was performed. MRI data were acquired as overlapping stacks of two-dimensional (2D) images. The images were processed with a bespoke open-source reconstruction algorithm to produce a super-resolution three-dimensional (3D) volume of the fetal thorax. These data were assessed with measurement comparison with paired 2D ultrasound, structured anatomical assessment of the 2D and 3D data, and contemporaneous, archived clinical fetal MRI reports, which were compared with postnatal findings after delivery.
Results:
A total of 85 patients underwent fetal MRI during the study period. The mean gestational age at the time of MRI was 32 weeks (range 24-36 weeks). Paired echocardiography data were available in 51 cases. Vascular measurements showed good agreement with 2D echocardiography (intraclass correlation coefficient, 0.78; 95% confidence interval, 0.64-0.84). Fetal vascular structures were more effectively visualized with 3D MRI than with uncorrected 2D MRI (657 [97%] of anatomical areas identified vs. 358 [53%] of 680 areas; p < 0.0001). Observers gave a higher diagnostic quality score for 3D data (90%) of cases with 10% of scores tied with 2D data. Additional anatomical features were described in 10 cases, all of which were confirmed postnatally.
Conclusions:
The authors concluded that fetal MRI with open-source imaging processing software is a reliable method of generating high-resolution 3D imaging of the fetal vasculature.
Perspective:
Fetal echocardiography has been the mainstay of prenatal cardiac imaging since the 1980s. Even in experienced hands, optimal visualization of extracardiac structures such as aortic arch anatomy, pulmonary veins, and pulmonary arteries/collaterals remains a challenge. Maternal body habitus and fetal position also impact the quality of fetal imaging with echocardiography. While MRI has had an expanding role in the imaging of various fetal structures, prenatal cardiac MRI has been significantly limited by fetal motion. This study demonstrated a technique of imaging processing that significantly enhanced imaging of the fetal vasculature. Prenatal MRI appears to be a promising complementary modality for imaging the fetal cardiovascular system. Further studies will be required to further compare MRI with fetal echocardiography and identify appropriate indications for MRI in the evaluation of the fetal cardiovascular system.
Clinical Topics: Congenital Heart Disease and Pediatric Cardiology, Noninvasive Imaging, Congenital Heart Disease, CHD and Pediatrics and Imaging, Echocardiography/Ultrasound, Magnetic Resonance Imaging
Keywords: Cardiac Imaging Techniques, Echocardiography, Fetal Heart, Fetus, Gestational Age, Heart Defects, Congenital, Imaging, Three-Dimensional, Magnetic Resonance Imaging, Ultrasonography
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