Factors influencing image quality in fetal cardiovascular magnetic resonance cine imaging using Doppler ultrasound gating: A multicenter study.

BACKGROUND: Fetal cine cardiovascularmagnetic resonance (CMR) is an emerging technique for evaluating the fetal heart in conditions such as congenital heart disease, but limited evidence on factors affecting image quality restricts its clinical potential. This study investigated key determinants of image quality in a multicenter cohort.

METHODS: This study analyzed fetal CMR scans from April 2021 to July 2023 at three centers (University Hospital Bonn, Children's Hospital Colorado, Phoenix Children's Hospital). Cine image quality was assessed using a 5-point Likert scale (1=non-diagnostic to 5=excellent) across three criteria as follows: contour sharpness, blood-to-structure contrast, and artifacts. Overall image quality scores were calculated by the average of all criteria. Apparent signal-to-noise (aSNR) and contrast-to-noise ratios (aCNR) were measured. Nine parameters were evaluated for their impact on image quality, namely: gestational age, body mass index (BMI), fetal motion, patient positioning, gating signal stability, breathing technique, field strength, slice thickness, and flip angle. Comparisons were conducted using the Mann-Whitney U test.

RESULTS: A total of 98 scans were analyzed. Higher overall image quality, aSNR, and aCNR were observed in participants with BMI <30 kg/m², gestational age ≥32 weeks, low fetal motion severity, and stable gating signals (e.g., overall image quality for BMI <30 kg/m² vs ≥30 kg/m²: 4.4±0.7 vs. 4.1±0.7, p<0.001). Supine positioning resulted in better overall image quality compared to the left lateral position (4.5±0.5 vs. 4.2±0.8, p=0.001). Breath-holds provided similar overall image quality but improved contour sharpness and reduced artifacts compared to free breathing (5 [4,5] vs. 4 [4,5], p=0.042; and 4 [3-5] vs. 4 [3-5], p=0.014, respectively). At 1.5T field strength, higher contrast and fewer artifacts were observed compared to 3T (5 [4,5] vs. 5 [4,5], p=0.041; and 4 [4,5] vs. 4 [3-5], p=0.010, respectively). Slice thickness showed no significant impact on image quality.

CONCLUSION: Various factors (e.g. BMI) influence fetal cardiac cine MRI image quality. Understanding these factors may help achieving reliable examinations and better exploit the potential of fetal cardiac MRI in clinical routine.