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Purpose: To ultimately make accurate and precise fetal noninvasive oxygen saturation (sO2) measurements by T2‐prepared bSSFP more widely available by systematically assessing error sources in order to potentially reduce perinatal mortality in cardiovascular malformations and fetal growth restriction. Methods: T2‐prepared bSSFP data were acquired in phantoms; in flowing blood in adults in the superior sagittal sinus, ascending and descending aorta, and main pulmonary artery; and in the fetal descending aorta and umbilical vein. T2 was assessed in relation to T2 two‐ or three‐parameter curve‐fitting techniques, SSFP readout, refocusing time delay (τ), constant and pulsatile blood flow, and impact of T1 recovery. Further, fetal T2 and sO2 variability were quantified in the descending aorta and umbilical vein in healthy fetuses and fetuses with cardiovascular malformation (gestational weeks 32–38). Results: In phantoms, three‐parameter fitting was accurate irrespective of phase FOV (<4 ms; i.e., <2%), and T2 was overestimated (up to 23 ms/10%; p = 0.001) beyond ±30 Hz off‐resonance. In the adult aorta, T2 was underestimated during higher blood flow velocities and pulsatility for τ = 16 ms (−41 ms/−17%; p = 0.008). In fetuses, two‐parameter fitting overestimated T2 compared with three‐parameter fitting (+33 ms/+18%; p = 0.03). T2 variability was 18 ms/15% in the fetal descending aorta and 28 ms/14% in the umbilical vein. The resulting estimated sO2 variability was ∼10% (15% of sO2 value) in the fetal descending aorta. Conclusions: Errors due to T2‐fitting techniques, off‐resonance, flow velocity, and insufficient T1 recovery between image acquisitions could be mitigated by using three‐parameter fitting with included saturation‐prepared images approximating infinite T2‐preparation time, adequate shimming covering the fetus and placenta, and by modifying acquisition parameters. Variability in fetal blood T2 and sO2, however, indicate that it is currently not feasible to use these methods for prediction of disease. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 [ABSTRACT FROM AUTHOR]

Results demonstrate that a spatial gradient of phosphorylated myosin light chain across the heart brings about torsion, which facilitates blood to wrung and get pumped out of the heart. Data indicate that cardiac contraction occurs due to inverse alteration of torsion and stretch activation response.