Purpose or Case Report: The purpose of this study is to report visualization rates for standard cardiac axial views by FCMR using a prospective ECG pseudogating method and compare visualization rates for acquisitions performed in 1.5 and 3T. Secondary aims include a comparison of image quality between 2 observers and between 1.5 and 3T. Specific absorption rates (SAR) are also compared.
Methods & Materials: 118 fetuses underwent 119 FCMR examinations gated by an external ECG simulator (PS410 ECG simulator, Fluke Biomedical, Cleveland, OH). Images were obtained using balanced steady-state free precession sequences. Visualization rates for axial anatomical planes from stomach to superior mediastinum were compared between 1.5T and 3T and between 2 different examiners. Perceived image quality was rated using a 1-5 Likert scale (5=superb, 4=good, 3=reasonable, still of diagnostic quality, 2=poor, and 1=non-diagnostic) and compared between 1.5 and 3T and between examiners. Statistical analysis was performed using the student-t test, Wilcoxon rank-sum test, chi-square test and Fisher’s exact test as appropriate.
Results: The left ventricle (LV) (76.7%), right ventricle (RV) (76.3%), 4-chamber view (4CH) (76.1%), right atrium (RA) (66.8%), left atrium (LA) (66.8%), ventricular septum (IVS) (66.6%), superior vena cava (SVC) (61.6%) and ductus arteriosus (PDA) (60.1%) had the highest confident visualization rates in normal and abnormal cases. There was a statistically significant difference in visualization rates for cardiac structures between 1.5 and 3T: 4CH 82.6% vs 53.7%, LV 82.3% vs 57.4%, RV 81.5% vs 58%, LA and RA 72.3% vs 48.2%, SVC 70.1% vs 54.6%, PDA 63.3% vs 45.4% (p< 0.001) for all comparisons. Overall perceived image quality score was 3.31 ± 0.95 for reviewer 1 and 3.27 ± 1.05 for reviewer 2 (p=0.85); however there was a significant difference in image quality score between 1.5 and 3T (3.38 ± 0.97 vs 2.57 ± 0.93 (p<0.001). SAR was not different between the 2 magnets (0.89 ± 0.89 and 1.02 ± 0.73, p=0.48).
Conclusions: Standard cardiac axial planes can be obtained by FCMR with reasonable image quality. As image quality and visualization rates for anatomical structures are significantly higher at 1.5T, this should be the magnet of choice for fetal cardiac imaging.