Background Fetal cardiac magnetic resonance imaging (MRI) improves the diagnosis of congenital heart defects, but is sensitive to fetal motion due to long image acquisition time. This may be overcome with faster image acquisition with low resolution, followed by image enhancement to provide clinically useful images. Purpose To combine phase‐encoding undersampling with super‐resolution neural networks to achieve high‐resolution fetal cine cardiac MR images with short acquisition time. Study Type Prospective. Subjects Twenty‐eight fetuses (gestational week 36 [interquartile range 33–38 weeks]). Field Strength/Sequence 1.5 T, balanced steady‐state free precession (bSSFP) cine sequence. Assessment Images were acquired using fully sampled Doppler ultrasound‐gated clinical bSSFP cine as reference, with equivalent cine sequences with decreased phase‐encoding resolution (25%, 33%, and 50% of clinical standard). Two super‐resolution methods based on convolutional neural networks were proposed and evaluated (phasrGAN and phasrresnet). Data were partitioned into training (36 cine slices), validation (3 cine slices), and test sets (67 cine slices) without overlap. Conventional reconstruction methods using bicubic interpolation and k‐space zeropadding were used for comparison. Three blinded observers scored image quality between 1 and 10. Statistical Tests Image scores are reported as median [interquartile range] and were compared using Mann–Whitney's nonparametric test with P < 0.05 showing statistically significant differences. Results Both proposed methods showed no significant difference in image quality compared to clinical images (8 [7–8.5]) down to 33% (phasrGAN 8 [6.5–8]; phasrresnet 8 [7–8], all P ≥ 0.19) phase‐encoding resolution, i.e., up to three times faster image acquisition, whereas bicubic interpolation and k‐space zeropadding showed significantly lower quality for 33% phase‐encoding resolution (both 7 [6–8]). Data Conclusion Super‐resolution enhancement can be used for fetal cine cardiac MRI to reduce image acquisition time while maintaining image quality. This may lead to an improved success rate for fetal cine MR imaging, as the impact of fetal motion is lessened by shortened acquisitions. Level of Evidence 1 Technical Efficacy Stage 2

Background Mild hypothermia, 32-35°C, reduces infarct size in experimental studies, potentially mediating reperfusion injuries, but human trials have been ambiguous. To elucidate the cardioprotective mechanisms of mild hypothermia, we analyzed cardiac performance in a porcine model of ischemia/reperfusion, with serial cardiovascular magnetic resonance (CMR) imaging throughout one week using non-invasive pressure-volume loops. Methods and results Normothermia and Hypothermia groups sessions (n=7+7 pigs, nonrandom allocation) were imaged with CMR at baseline and subjected to 40 minutes of normothermic ischemia by catheter intervention. Thereafter, the Hypothermia group was rapidly cooled (mean 34.5°C) for 5 minutes before reperfusion. Additional CMR sessions at two hours, 24 hours, and seven days acquired ventricular volumes and ischemic injuries (unblinded analysis). Stroke volume (-24%; p=0.029; Friedmans test) and ejection fraction (-20%; p=0.068) were notably reduced at 24h in the Normothermia group compared to baseline. In contrast, the decreases were ameliorated in the Hypothermia group (stroke volume: -6%; p=0.77; ejection fraction: -6%; p=0.13). Mean arterial pressure remained stable in Normothermic animals (-3%, p=0.77) but dropped two hours post-reperfusion in hypothermic animals (-18%, p=0.007). Both groups experienced a decrease and partial recovery pattern for PV loop-derived variables over one week, but the adverse effects tended attenuated in the Hypothermia group. Infarct sizes were 10±8% in Hypothermic and 15±8% in Normothermic animals (p=0.32). Analysis of covariance at 24 hours indicated that hypothermia has cardioprotective properties incremental to reducing infarct size, such as higher external power (p=0.061) and lower arterial elastance (p=0.015). Conclusion Using non-invasive pressure-volume loops by CMR, we observed that mild hypothermia at reperfusion alleviates the heart’s work after ischemia/reperfusion injuries during the first week and preserves short-term cardiac performance. This hypothesis-generating study suggests hypothermia to have cardioprotective properties, incremental to reducing infarct size. The primary cardioprotective mechanism was likely an afterload reduction acutely unloading the left ventricle.

Purpose To explore a fetal 3D cardiovascular cine acquisition using a radial image acquisition and compressed‐sensing reconstruction and compare image quality and scan time with conventional multislice 2D imaging. Methods Volumetric fetal cardiac data were acquired in 26 volunteers using a radial 3D balanced SSFP pulse sequence. Cardiac gating was performed using a Doppler ultrasound device. Images were reconstructed using a parallel‐imaging and compressed‐sensing algorithm. Multiplanar reformatting to standard cardiac views was performed before image analysis. Clinical 2D images were used for comparison. Qualitative and quantitative image evaluation were performed by two experienced observers (scale: 1–4). Volumes, mass, and function were assessed. Results Average scan time for the 3D imaging was 6 min, including one localizer. A 2D imaging stack covering the entire heart including localizer sequences took at least 6.5 min, depending on planning complexity. The 3D acquisition was successful in 7 of 26 subjects (27%). Overall image contrast and perceived resolution were lower in the 3D images. Nonetheless, the 3D images had, on average, a moderate cardiac diagnostic quality (median [range]: 3 [1–4]). Standard clinical 2D acquisitions had a high cardiac diagnostic quality (median [range]: 4 [3, 4]). Cardiac measurements were not different between 2D and 3D images (all p > 0.16). Conclusion The presented free‐breathing whole‐heart fetal 3D radial cine MRI acquisition and reconstruction method enables retrospective visualization of all cardiac views while keeping examination times short. This proof‐of‐concept work produced images with diagnostic quality, while at the same time reducing the planning complexity to a single localizer.